refactor(tools): group the sixty scripts by what they talk to

One directory with sixty scripts stopped being navigable, and the grouping is also the sandbox boundary:

  Tools/unreal/    commandlets and the two map builders, with ue_common.py and ue_placement.py as the
                   shared imports (they need the engine)
  Tools/blender/   builders, exporters, the FBX preset, the MPFB character pipeline, blender_screenshots
                   (they need the Blender Flatpak)
  Tools/review/    the visual loop: render_screenshots.sh, judge_screenshot.py, hero_compare.py,
                   build_comparison_md.py, e2e_asset_check.py, hero_iterate.sh, visual_loop.py,
                   visual_targets.json
  Tools/gen/       image and texture generation: the ComfyUI driver, deterministic texture writers,
                   reference fetching
  Tools/input/     OS-level input injection
  root             _common.py, check-lfs.sh, addon_compat_probe.py, sibling_asset_audit.py, tests/

Every moved script now resolves the repository root as ../.. and puts the tools root plus its siblings on
sys.path, so 'import ue_common' still works from unreal/. The test suite bootstrap does the same for the five
folders. render_screenshots.sh takes the folder as a third argument to run_cmdlet, and the e2e driver,
hero_iterate.sh and the comparison generator were repointed.

51 README rows now link to their new location, the README gains a Layout section naming each folder's
sandbox, and the architecture notes and Blender README follow the moves.

Verified: 108 tests pass, prettier is clean, judge_screenshot.py and hero_compare.py run from their new
homes, and the e2e run was aborted mid-way (it had been rebuilding an empty DemoMap for 15 minutes) and is
being rerun against the new layout.

Tools/blender/comfyui_character_blueprint.py

@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+"""Generate character blueprints with the local ComfyUI instance.
+
+A "blueprint" here is an art-direction sheet for one character: a front, side and back
+view, plus a head detail, generated from a fixed prompt and seed set so the sheet can
+be regenerated and compared against later. It is the reference the modelled character
+is evaluated against — see `Tools/blender/character_match.py`.
+
+    python3 Tools/blender/comfyui_character_blueprint.py \
+        --character "GigLine walker" \
+        --desc "lean adult pedestrian, short dark hair, olive skin, plain navy t-shirt, dark jeans, worn sneakers" \
+        --out Art/characters/blueprints
+
+Writes one PNG per view plus `contact-sheet.png` and `blueprint.json`, which records
+the prompt, model, seeds and the ComfyUI prompt ids. Everything is generated locally
+by `Tools/gen/comfyui_generate.py`; no network service and no credential is involved.
+
+The sheet is generated art, not photography, and it stays out of the reference photo
+folders on purpose: AGENTS.md forbids committing reference photography, and a
+generated concept should not blur that line.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+import comfyui_generate as comfy  # noqa: E402
+
+from PIL import Image  # noqa: E402
+
+VIEWS = (
+    # name, prompt suffix, seed
+    ("front", "full body front view, neutral standing pose, arms at sides, "
+              "even studio light, plain light grey background, character sheet", 101),
+    ("side", "full body side profile view, neutral standing pose, arms at sides, "
+             "even studio light, plain light grey background, character sheet", 202),
+    ("back", "full body back view, neutral standing pose, arms at sides, "
+             "even studio light, plain light grey background, character sheet", 303),
+    ("head", "head and shoulders portrait, front view, neutral expression, "
+             "even studio light, plain light grey background", 404),
+)
+NEGATIVE = ("multiple people, crowd, text, watermark, signature, blurry, low quality, "
+            "cropped limbs, extra limbs, deformed hands, cartoon, anime, logo")
+
+
+def contact_sheet(paths, out_path, columns=4):
+    images = [Image.open(p).convert("RGB") for p in paths if os.path.exists(p)]
+    if not images:
+        return None
+    width = max(i.width for i in images)
+    height = max(i.height for i in images)
+    sheet = Image.new("RGB", (width * columns, height), (24, 24, 24))
+    for index, image in enumerate(images[:columns]):
+        sheet.paste(image.resize((width, height)), (index * width, 0))
+    sheet.save(out_path)
+    return out_path
+
+
+def main(argv=None):
+    ap = argparse.ArgumentParser(description=__doc__,
+                                 formatter_class=argparse.RawDescriptionHelpFormatter)
+    ap.add_argument("--character", default="GigLine walker")
+    ap.add_argument("--desc", required=True,
+                    help="what the character wears and looks like; drives every view")
+    ap.add_argument("--out", default="Art/characters/blueprints")
+    ap.add_argument("--model", default=comfy.DEFAULT_MODEL)
+    ap.add_argument("--size", default="832x1216")
+    ap.add_argument("--steps", type=int, default=30)
+    ap.add_argument("--cfg", type=float, default=5.0)
+    args = ap.parse_args(argv)
+
+    if not os.path.isdir(comfy.HOST) and "://" not in comfy.HOST:
+        print(f"error: bad COMFYUI_HOST {comfy.HOST}", file=sys.stderr)
+        return 2
+
+    os.makedirs(args.out, exist_ok=True)
+    width, height = (int(v) for v in args.size.lower().split("x"))
+
+    record = {"character": args.character, "description": args.desc,
+              "model": args.model, "views": {}}
+    written = []
+    for name, suffix, seed in VIEWS:
+        prompt = f"{args.character}, {args.desc}, {suffix}"
+        out = os.path.join(args.out, f"{name}.png")
+        graph = comfy.workflow(prompt, NEGATIVE, args.model, width, height, seed,
+                               args.steps, args.cfg, "dpmpp_2m", "karras")
+        queued = comfy.post("/prompt", {"prompt": graph})
+        prompt_id = queued.get("prompt_id")
+        if not prompt_id:
+            print(f"error: ComfyUI rejected the {name} prompt: {queued}", file=sys.stderr)
+            return 1
+        print(f"{name}: queued {prompt_id} (seed {seed})")
+        image = comfy.wait_for_image(prompt_id, timeout=600.0)
+        if image is None:
+            print(f"error: no image for {name}", file=sys.stderr)
+            return 1
+        with open(out, "wb") as handle:
+            handle.write(image)
+        record["views"][name] = {"file": out, "seed": seed, "prompt": prompt,
+                                 "negative": NEGATIVE, "prompt_id": prompt_id}
+        written.append(out)
+
+    sheet = contact_sheet(written, os.path.join(args.out, "contact-sheet.png"))
+    record["contact_sheet"] = sheet
+    record["note"] = ("generated locally by Tools/blender/comfyui_character_blueprint.py; "
+                      "record the model licence in THIRD_PARTY_NOTICES.md before shipping")
+    with open(os.path.join(args.out, "blueprint.json"), "w") as handle:
+        json.dump(record, handle, indent=2)
+    print(f"wrote {len(written)} views + contact sheet -> {args.out}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())