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.