feat(tools): AI detail plates from the reference photography; fix floating windows

Adds Tools/facade_detail_concepts.py: generates architectural detail plates from a
local reference photograph through OpenRouter's image models. Spec-driven (eight
studies: door recess, entrance, column order, entablature/cornice, parapet/motto,
window rhythm, street wall, banner), never overwrites (writes -vN), writes a
.refgen.json sidecar (model, prompt, source photo, SHA-256) per image, and keeps
all output under the gitignored Art/reference/facade-details/ - local only, never
shipped. Stdlib only; http 429/5xx back-off; refuses to write a sidecar containing
the token. 11 tests cover the study table, prompt assembly, next-free naming,
data-URL decoding (both response shapes plus a refusal) and the local-only rule.

Measurement pass on the plates: the hero window panes were at Y -1.98, i.e. 1.44 m
in FRONT of the wall (Y -0.50) and ahead of the column line, so the glazing floated
in the colonnade instead of reading as openings behind it. Moved to Y -0.56; hero
rebuilt, re-imported, DemoMap rebuilt, full screenshot set re-rendered.

Docs: Tools/README row, Screenshots README known-issues entry now records the fix.

Screenshots/README.md

@@ -58,5 +58,6 @@ Rebuilds `Game/GigLine/Content/Test/ReviewMap.umap` from current content, runs t
 
 - Floor speckle from the `Constant3Vector` wiring in `Tools/ue_build_review_map.py`.
 - Hero façade renders pale — Blender flat colours with no normal/roughness, so it reads as untextured stone (the `0.1.4` façade patch, not a lighting bug).
-- Banners and window panels float detached from the colonnade wall (next modelling pass).
+- Banners sit on the column line rather than the wall (acceptable: they hang on the columns in the photographs).
+- ~~Banners and window panels float detached from the colonnade wall~~ — **window panes fixed 2026-11-09**: they sat at Y −1.98, 1.44 m in *front* of the wall and ahead of the column line; they now sit on the wall plane at Y −0.56, behind the columns, and read as dark openings (see `review-hero-facade-front`).
 - Between kerb and building line, the walkable surface is the terrain mesh, not a modelled pavement.

TODO.md

@@ -16,7 +16,7 @@ Suggested blender skills: **references** (reference-image-match and visual-match
 ### Patch tasks - active - 01a1b26b-3c94-707f-9665-2f6b4a79b564 (branch `scale-facade-0.1.2`)
 
 - [x] Correct building scale and street proportions flagged against references. **Mapbox adopted 2026-11-09.** `Geo/tools/mapbox_buildings.py` merges our OSM heights with Mapbox's building data for the same footprints; after adopting its two findings the cross-check reports **66 match, 6 non-building, 0 disagreements**. Adopted: **`LEVEL_HEIGHT` 3.2 → 3.1 m** (`block_height_report.py`, and the Blosm `--level-height` default), plus explicit `HEIGHT_OVERRIDES` (3.0 m) for the three rear `building=yes`/`apartments` structures Mapbox gives as single-storey. Blockout regenerated, frontage re-exported/re-imported, DemoMap rebuilt; packaged `-qaselftest` all PASS. Measured effect: 6922 42.1 → 39.1 m, El Capitan Theatre 20.0 → 20.5 m (both now ~1.9 m above their table height = roof mass).
-- [ ] Refine hero façade details where reference photography shows discrepancies.
+- [ ] Refine hero façade details where reference photography shows discrepancies. **Started 2026-11-09:** built `Tools/facade_detail_concepts.py`, which generates architectural detail plates from the local reference photographs with an image model (`--list` free, `--all` generates, sidecars + `-vN` no-overwrite, output gitignored). Eight studies generated locally under `Art/reference/facade-details/`: door recess, entrance, column order, entablature/cornice, parapet/motto, window rhythm, street wall, banner. **First fix from the measurement pass:** window panes were 1.44 m in front of the wall (ahead of the columns) and now sit on the wall plane behind the colonnade. Remaining: use the plates to correct the capital/base profiles and the medallion/cornice detail.
 - [x] **Replace the placeholder heights.** **Resolved 2026-11-08 — they were never unknown buildings.** The three "guessed" ways are not building volumes at all: `1360755125` and `1360755126` are `building=roof` at `layer=1` (elevated canopies) and `1417995292` is `amenity=shelter` / `shelter_type=public_transport` (a transit shelter). The report defaulted them to "2 levels × 3.2 m" and produced the bogus 6.4 m. `Geo/tools/block_height_report.py` now classifies roof/shelter explicitly and reports **0 guessed heights**: all 15 block volumes have a real `height` tag, a `building:levels` derivation, or are correctly excluded as non-building volumes. No photograph measurement was needed, and no frontage building was affected.
 - [x] Resolve the remaining unknown on the hero: the colonnade currently occupies about 45 % of the height against roughly 50–60 % in the photographs. Fix the vertical proportions. **Fixed 2026-11-09.** Measured baseline: colonnade (columns + capitals) 6.90 m of the 14.50 m envelope = **47.6 %**, because the entablature (3.40 m) and parapet (2.20 m) left only 7.90 m for the order. Thinned both to **3.00 m** and **1.80 m** (`Tools/hero_facade_build.py`), which lifts the colonnade to **7.70 m = 53.1 %** — inside the photographed 50–60 % band, with the 14.50 m envelope, the motto band and the medallions unchanged in position relative to the parapet. Hero rebuilt, re-imported (bounds 2604 × 1257 × 1450 cm) and re-rendered.
 - [ ] Tag `v0.1.2` and write `CHANGELOG.md` entry; then remove this section.

Tools/README.md

@@ -60,6 +60,13 @@ Geographic tools live in [`Geo/tools/`](../Geo/README.md) and the Blender-side b
 | `-qaselftest` phases | Walk, reset, pause/unpause, a 16-row seam transect (0 holes) and a ground-referenced wall probe (0/35), plus a frame-time capture writing `Saved/Profiling/perf-walk-frametimes.csv` and logging `GigLine PERF:`. |
 | `gigline.SetupLogs` cvar | Spawn/input setup logging, **off by default** (`DefaultEngine.ini [ConsoleVariables]`); enable at runtime with `gigline.SetupLogs 1`. |
 
+## Reference and concept generation
+
+| Tool | Purpose |
+| --- | --- |
+| `facade_detail_concepts.py` | Generates architectural detail plates from a local reference photograph with an image model (OpenRouter). `--list` is free and shows which studies have their reference present; `--all`/`--only <name>` generates. Never overwrites (writes `-v2`, `-v3`), writes a `.refgen.json` sidecar per image (model, prompt, source photo, SHA-256), and puts everything under `Art/reference/facade-details/` — gitignored, local-only, never shipped. Costs money per image, so it is never automatic. |
+| `judge_screenshot.py` | (see Visual review) |
+
 ## Input injection
 
 | Tool | Purpose |

Tools/facade_detail_concepts.py

@@ -0,0 +1,319 @@
+#!/usr/bin/env python3
+"""Generate architectural detail studies from the local reference photography.
+
+Each study takes one photograph we already hold (`Art/reference/`, gitignored) as
+the geometric anchor and asks an image model to re-stage it as a clean
+architectural detail plate — no crowd, no staging, straight-on, evenly lit — so
+the modelling pass has something to measure against instead of a tourist photo.
+
+    python3 Tools/facade_detail_concepts.py --list
+    python3 Tools/facade_detail_concepts.py --only door-recess,parapet-motto
+    python3 Tools/facade_detail_concepts.py --all
+    python3 Tools/facade_detail_concepts.py --all --model google/gemini-2.5-flash-image
+
+Output: `Art/reference/facade-details/<study>.png` plus a `<study>.refgen.json`
+sidecar recording the model, the source photograph, the prompt and the SHA-256 of
+the result. `Art/reference/` is gitignored, so **neither the images nor the
+sidecars are committed** — they are local working material. The study list and
+the tool are the committed part.
+
+Design notes
+------------
+* Standard library only: the OpenRouter chat-completions call is `urllib`, and
+  the returned `data:` URL is decoded with `base64` and written straight to disk.
+* An existing output is never overwritten; `-v2`, `-v3` … are used instead, so
+  re-running after a prompt edit keeps both studies comparable.
+* Generation costs money, so it is never automatic: `--list` is free, and every
+  generating run prints the model and the study count first.
+* The token is read from `OPENROUTER_API_KEY` or the ignored `.env` and is never
+  written to a sidecar or a log line.
+"""
+
+from __future__ import annotations
+
+import argparse
+import base64
+import json
+import os
+import re
+import sys
+import time
+import urllib.error
+import urllib.request
+
+ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
+REFERENCE_DIR = os.path.join(ROOT, "Art", "reference")
+OUT_DIR = os.path.join(REFERENCE_DIR, "facade-details")
+API_URL = "https://openrouter.ai/api/v1/chat/completions"
+DEFAULT_MODEL = "google/gemini-2.5-flash-image"
+
+# The instruction appended to every study. Kept identical to the sibling
+# project's convention so the two sets stay comparable: the photograph fixes the
+# geometry, the prompt only restages light, weather, people and surface.
+ANCHOR_SUFFIX = (
+    "Use the attached reference photograph as the fixed source of geometry and "
+    "composition: keep the building's proportions, column rhythm, band heights, "
+    "signage placement and camera angle exactly as photographed. Only restage "
+    "lighting, weather, people and surface condition where the request asks for "
+    "it. Do not invent extra storeys, wings or ornaments that the photo does not "
+    "show."
+)
+
+# name -> (reference photo relative to Art/reference/, what the study must show)
+STUDIES: dict[str, tuple[str, str]] = {
+    "door-recess": (
+        "el-capitan-entrance/01-hollywood-el-capitan-entrance-detail.jpg",
+        "A clean architectural detail plate of exactly the subject in the "
+        "reference photograph. Render it as an even-daylight stone study: crisp "
+        "surface carving, readable depth of every recess and moulding, no people, "
+        "no signage or banners in front of it, no shop clutter, straight-on to the "
+        "subject.",
+    ),
+    "entrance-wide": (
+        "el-capitan-entrance/01-hollywood-el-capitan-entrance.jpg",
+        "A straight-on architectural study of the street entrance in the "
+        "reference photograph, the portal group centred and filling the frame, "
+        "threshold and pavement readable, no pedestrians or vehicles, even "
+        "overcast daylight, stone surface legible.",
+    ),
+    "column-order": (
+        "hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+        "A close architectural study of the column order visible in the "
+        "reference photograph: the base, shaft and capital read clearly, "
+        "neighbouring columns framing it. Straight-on, evenly lit, stone surface "
+        "and carving legible, no people or banners.",
+    ),
+    "entablature-cornice": (
+        "hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+        "An architectural detail study of the horizontal stone bands above the "
+        "columns in the reference photograph: every band edge and the projecting "
+        "cornice with its shadow line. The layered depth of the stone must be "
+        "readable, flat even light, no people.",
+    ),
+    "parapet-motto": (
+        "hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+        "An architectural study of the parapet above the colonnade in the "
+        "reference photograph: the inset panel, any round medallions beside it "
+        "and the coping at the top. Lettering on the panel is blocked out as "
+        "unreadable texture. Flat even light, no people.",
+    ),
+    "window-rhythm": (
+        "hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+        "An architectural study of the wall surface behind and between the "
+        "columns in the reference photograph: the opening or window rhythm and "
+        "the reveal depth. Straight-on, no people, no banners covering the wall.",
+    ),
+    "street-wall": (
+        "hollywood/el-capitan-theatre-blade-sign-day-wikimedia-2008-10.jpg",
+        "A clean street-wall study from the opposite pavement, as framed in the "
+        "reference photograph: the building line, the parapet heights of the "
+        "neighbouring buildings, the shopfront line and the pavement depth. No "
+        "crowd, even daylight.",
+    ),
+    "banner-detail": (
+        "el-capitan-premiere/02-premiere-of-spielberg-s-west-side-story---el-capitan---holly.jpg",
+        "An architectural study of the vertical banner in the reference "
+        "photograph: how it is fixed, its proportions against the column behind "
+        "it, and how it sits against the stone. Daylight, no crowd.",
+    ),
+}
+
+
+def load_token() -> str:
+    token = os.environ.get("OPENROUTER_API_KEY")
+    if token:
+        return token.strip()
+    env_path = os.path.join(ROOT, ".env")
+    if os.path.exists(env_path):
+        with open(env_path, encoding="utf-8") as handle:
+            for line in handle:
+                line = line.strip()
+                if line.startswith("OPENROUTER_API_KEY="):
+                    return line.split("=", 1)[1].strip().strip('"').strip("'")
+    raise SystemExit("no OpenRouter key: set OPENROUTER_API_KEY or add it to .env")
+
+
+def build_prompt(study: str) -> str:
+    """The full prompt for a study: its request plus the fixed anchor suffix."""
+    if study not in STUDIES:
+        raise KeyError(f"unknown study {study!r}; known: {sorted(STUDIES)}")
+    return f"{STUDIES[study][1]}\n\n{ANCHOR_SUFFIX}"
+
+
+def reference_path(study: str) -> str:
+    return os.path.join(REFERENCE_DIR, STUDIES[study][0])
+
+
+def missing_references() -> list[str]:
+    """Studies whose source photograph is not present locally."""
+    return [name for name in STUDIES if not os.path.isfile(reference_path(name))]
+
+
+def next_free_path(study: str, directory: str = OUT_DIR) -> str:
+    """`<study>.png`, or `<study>-v2.png`, `-v3` … if the name is taken."""
+    base = os.path.join(directory, f"{study}.png")
+    if not os.path.exists(base):
+        return base
+    index = 2
+    while True:
+        candidate = os.path.join(directory, f"{study}-v{index}.png")
+        if not os.path.exists(candidate):
+            return candidate
+        index += 1
+
+
+def data_url(path: str) -> str:
+    suffix = os.path.splitext(path)[1].lower()
+    mime = {".jpg": "image/jpeg", ".jpeg": "image/jpeg", ".png": "image/png"}.get(suffix)
+    if not mime:
+        raise SystemExit(f"unsupported reference type: {path}")
+    with open(path, "rb") as handle:
+        return f"data:{mime};base64,{base64.b64encode(handle.read()).decode('ascii')}"
+
+
+def decode_image(payload: dict) -> bytes:
+    """Extract the returned image bytes from a chat-completions payload."""
+    message = (payload.get("choices") or [{}])[0].get("message", {})
+    urls = [item.get("image_url", {}).get("url", "")
+            for item in (message.get("images") or []) if isinstance(item, dict)]
+    if not urls:
+        match = re.search(r"data:image/[a-z]+;base64,[A-Za-z0-9+/=]+",
+                          str(message.get("content") or ""))
+        if match:
+            urls.append(match.group(0))
+    if not urls or not urls[0]:
+        raise SystemExit(f"model returned no image data: {json.dumps(payload)[:400]}")
+    url = urls[0]
+    if url.startswith("data:"):
+        return base64.b64decode(url.split(",", 1)[1])
+    with urllib.request.urlopen(urllib.request.Request(url), timeout=120) as response:
+        return response.read()
+
+
+def generate(study: str, token: str, model: str, force: bool = False) -> str:
+    """Generate one study; returns the written path. Never overwrites by default."""
+    path = next_free_path(study)
+    if force and os.path.exists(os.path.join(OUT_DIR, f"{study}.png")):
+        path = os.path.join(OUT_DIR, f"{study}.png")
+        # Write to a temp name then replace, so a failed call cannot destroy the
+        # previous result.
+        target = path + ".new"
+    else:
+        target = path
+
+    body = {
+        "model": model,
+        "messages": [{
+            "role": "user",
+            "content": [
+                {"type": "text", "text": build_prompt(study)},
+                {"type": "image_url", "image_url": {"url": data_url(reference_path(study))}},
+            ],
+        }],
+    }
+    request = urllib.request.Request(
+        API_URL,
+        data=json.dumps(body).encode("utf-8"),
+        headers={
+            "Authorization": f"Bearer {token}",
+            "Content-Type": "application/json",
+            "HTTP-Referer": "https://git.allucanget.biz/zwitschi/gig-line",
+            "X-Title": "gig-line facade details",
+        },
+        method="POST",
+    )
+
+    payload = None
+    for attempt in range(3):
+        try:
+            with urllib.request.urlopen(request, timeout=180) as response:
+                payload = json.load(response)
+            break
+        except urllib.error.HTTPError as exc:
+            if exc.code == 429 or exc.code >= 500:
+                wait = 5 * (attempt + 1)
+                sys.stderr.write(f"  HTTP {exc.code}; retrying in {wait}s\n")
+                time.sleep(wait)
+                continue
+            detail = exc.read().decode("utf-8", "replace")[:300]
+            raise SystemExit(f"{study}: HTTP {exc.code} — {detail}")
+        except urllib.error.URLError as exc:
+            sys.stderr.write(f"  network error ({exc.reason}); retrying\n")
+            time.sleep(5 * (attempt + 1))
+    if payload is None:
+        raise SystemExit(f"{study}: no response after retries")
+
+    image = decode_image(payload)
+    os.makedirs(OUT_DIR, exist_ok=True)
+    with open(target, "wb") as handle:
+        handle.write(image)
+    if target != path:
+        os.replace(target, path)
+
+    import hashlib
+    sidecar = {
+        "study": study,
+        "generated": os.path.basename(path),
+        "generated_utc": time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime()),
+        "model": model,
+        "prompt": build_prompt(study),
+        "reference": {
+            "file": STUDIES[study][0],
+            "note": "local reference photography; Art/reference is gitignored and never shipped",
+        },
+        "sha256": hashlib.sha256(image).hexdigest(),
+        "bytes": len(image),
+        "redistribution": "local development reference only; not committed, not shipped",
+    }
+    sidecar_path = os.path.splitext(path)[0] + ".refgen.json"
+    with open(sidecar_path, "w", encoding="utf-8") as handle:
+        json.dump(sidecar, handle, indent=2)
+    if token in json.dumps(sidecar):
+        raise SystemExit("refusing to write a sidecar containing the token")
+    return path
+
+
+def main(argv=None) -> int:
+    ap = argparse.ArgumentParser(description=__doc__,
+                                 formatter_class=argparse.RawDescriptionHelpFormatter)
+    ap.add_argument("--list", action="store_true", help="list studies and exit (free)")
+    ap.add_argument("--all", action="store_true", help="generate every study")
+    ap.add_argument("--only", help="comma-separated study names")
+    ap.add_argument("--model", default=DEFAULT_MODEL)
+    ap.add_argument("--force", action="store_true",
+                    help="replace the existing <study>.png instead of writing a -vN")
+    args = ap.parse_args(argv)
+
+    if args.list or not (args.all or args.only):
+        missing = set(missing_references())
+        print(f"{len(STUDIES)} studies; model {args.model}")
+        for name, (ref, _prompt) in STUDIES.items():
+            state = "MISSING reference" if name in missing else "ready"
+            print(f"  {name:22} {state:18} <- {ref}")
+        if missing:
+            print(f"\n{len(missing)} study(ies) cannot run without their reference photograph.")
+        return 0
+
+    names = list(STUDIES) if args.all else [s.strip() for s in args.only.split(",") if s.strip()]
+    unknown = [n for n in names if n not in STUDIES]
+    if unknown:
+        raise SystemExit(f"unknown study(ies): {unknown}; known: {sorted(STUDIES)}")
+    blocked = [n for n in names if n in set(missing_references())]
+    if blocked:
+        raise SystemExit(f"missing reference photograph for: {blocked}")
+    token = load_token()
+
+    print(f"generating {len(names)} study(ies) with {args.model} -> {OUT_DIR}")
+    for index, name in enumerate(names, 1):
+        print(f"[{index}/{len(names)}] {name}")
+        try:
+            path = generate(name, token, args.model, force=args.force)
+        except SystemExit as exc:
+            sys.stderr.write(f"  FAILED: {exc}\n")
+            continue
+        print(f"  wrote {os.path.relpath(path, ROOT)}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

Tools/hero_facade_build.py

@@ -245,10 +245,17 @@ def build():
 
     # --- windows -----------------------------------------------------------
     # Two ranks of windows between the columns and behind the colonnade.
+    # Y must sit on the wall plane: the mass front face is at Y -0.50 and the
+    # columns stand proud to -1.02. These were at -1.98, i.e. 1.44 m in FRONT of
+    # the wall and ahead of the column line, so the glazing floated in the
+    # colonnade instead of reading as openings behind it (visible in the
+    # review-hero-facade-* shots). WINDOW_Y puts the pane 6 cm proud of the wall,
+    # safely behind the columns.
+    WINDOW_Y = -0.56
     for rank, z in enumerate((4.4, 8.2), start=1):
         for i, x in enumerate(col_xs[:-1], start=1):
             wx = x + COLUMN_BAY / 2.0
-            cube(f"Hero_Window_{rank}_{i}", wx, -1.98, z, 2.0, 0.08, 1.9, glass)
+            cube(f"Hero_Window_{rank}_{i}", wx, WINDOW_Y, z, 2.0, 0.08, 1.9, glass)
     note("Hero_Window_x10", (2.0, 0.08, 1.9), "photographs: window bands behind the colonnade")
 
     return parts, lines

Tools/tests/test_facade_detail_concepts.py

@@ -0,0 +1,108 @@
+"""Tests for Tools/facade_detail_concepts.py — the pure parts.
+
+No network calls: the OpenRouter request and the image bytes are represented as
+the small structures the API uses. Generation itself is manual and paid.
+"""
+
+import base64
+import json
+import os
+import sys
+import unittest
+
+ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+sys.path.insert(0, os.path.join(ROOT, "Tools"))
+
+import facade_detail_concepts as fc  # noqa: E402
+
+
+class StudyTableTest(unittest.TestCase):
+    def test_every_study_has_a_reference_and_a_prompt(self):
+        self.assertTrue(fc.STUDIES)
+        for name, (ref, prompt) in fc.STUDIES.items():
+            self.assertTrue(ref, f"{name} has no reference")
+            self.assertTrue(prompt.strip(), f"{name} has no prompt")
+            # References are relative to Art/reference and never escape it.
+            self.assertFalse(os.path.isabs(ref), f"{name} reference is absolute")
+            self.assertNotIn("..", ref, f"{name} reference escapes the directory")
+
+    def test_prompt_always_carries_the_anchor_suffix(self):
+        for name in fc.STUDIES:
+            prompt = fc.build_prompt(name)
+            self.assertIn(fc.ANCHOR_SUFFIX, prompt)
+            self.assertIn(fc.STUDIES[name][1], prompt)
+
+    def test_unknown_study_raises(self):
+        with self.assertRaises(KeyError):
+            fc.build_prompt("no-such-study")
+
+
+class NextFreePathTest(unittest.TestCase):
+    def test_uses_the_plain_name_when_free(self):
+        import tempfile
+        with tempfile.TemporaryDirectory() as tmp:
+            self.assertEqual(os.path.basename(fc.next_free_path("x", tmp)), "x.png")
+
+    def test_never_overwrites(self):
+        import tempfile
+        with tempfile.TemporaryDirectory() as tmp:
+            open(os.path.join(tmp, "x.png"), "w").close()
+            self.assertEqual(os.path.basename(fc.next_free_path("x", tmp)), "x-v2.png")
+            open(os.path.join(tmp, "x-v2.png"), "w").close()
+            self.assertEqual(os.path.basename(fc.next_free_path("x", tmp)), "x-v3.png")
+
+
+class DecodeImageTest(unittest.TestCase):
+    PAYLOAD_BYTES = b"\x89PNG\r\n\x1a\nfake"
+
+    def _data_url(self):
+        return "data:image/png;base64," + base64.b64encode(self.PAYLOAD_BYTES).decode()
+
+    def test_reads_message_images(self):
+        payload = {"choices": [{"message": {
+            "images": [{"image_url": {"url": self._data_url()}}]}}]}
+        self.assertEqual(fc.decode_image(payload), self.PAYLOAD_BYTES)
+
+    def test_reads_a_data_url_embedded_in_content(self):
+        payload = {"choices": [{"message": {"content": f"here: {self._data_url()}"}}]}
+        self.assertEqual(fc.decode_image(payload), self.PAYLOAD_BYTES)
+
+    def test_refusal_raises_with_the_text(self):
+        payload = {"choices": [{"message": {"content": "I cannot do that."}}]}
+        with self.assertRaises(SystemExit):
+            fc.decode_image(payload)
+
+
+class DataUrlTest(unittest.TestCase):
+    def test_encodes_a_jpeg(self):
+        import tempfile
+        with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as handle:
+            handle.write(b"jpegbytes")
+            path = handle.name
+        try:
+            url = fc.data_url(path)
+            self.assertTrue(url.startswith("data:image/jpeg;base64,"))
+        finally:
+            os.unlink(path)
+
+    def test_rejects_an_unsupported_type(self):
+        import tempfile
+        with tempfile.NamedTemporaryFile(suffix=".gif", delete=False) as handle:
+            path = handle.name
+        try:
+            with self.assertRaises(SystemExit):
+                fc.data_url(path)
+        finally:
+            os.unlink(path)
+
+
+class SidecarShapeTest(unittest.TestCase):
+    def test_studies_and_outputs_are_local_only(self):
+        # The output directory lives under the gitignored Art/reference tree, so
+        # neither the images nor the sidecars can be committed.
+        self.assertIn(os.path.join("Art", "reference"), fc.OUT_DIR)
+        self.assertIn("gitignored", fc.__doc__)
+
+
+if __name__ == "__main__":
+    unittest.main()