feat(hero): generate the stone albedo with the new texture tool, import it, wire it into the material

Used the workflow integration from the previous step for real: generated a warm limestone ashlar albedo
with two profiles compared (AlbedoBase 17.04 vs Krea-2 13.90, AlbedoBase won), saved it as
Art/textures/generated/T_FacadeAshlar_AI.png beside its provenance sidecar, and imported it to
/Game/Hollywood/Textures.

ue_hero_facade_import.py now imports that albedo and, for the two stone slots, builds a material with
TextureSampleParameter2D -> Multiply(tint) -> Base Color, tiling the UVs 6x, so the map carries the coursing
and the tint keeps the value inside the reference's range.

Two real bugs fixed on the way:

- the albedo path was resolved against unreal.Paths.project_dir() (Game/GigLine), not the repository root, so
  the import silently skipped;
- the authored materials were never saved - only the mesh was - so after a reload the slots pointed at
  nothing and the elevation fell back to one default colour.

Honest status: the nodes are verified present and saved (Constant3Vector, TextureSampleParameter2D,
TextureCoordinate, Multiply) and the source mesh has UVs, but the render still shows the flat tint. Recorded
in TODO.md with the next probe: read the compiled Base Color pin instead of the node list.

THIRD_PARTY_NOTICES.md gains the AlbedoBase row (commercial use, credit required).

THIRD_PARTY_NOTICES.md

@@ -51,3 +51,4 @@ Rules that still apply, because they are about shipped output rather than local
 | Terrain and street prototype | USGS 3DEP DEM, OSM data, project scripts | Public domain USGS data; OpenStreetMap data, local private use | Source manifests in `Geo/manifests/`. |
 | Hero façade blockout | Project-owned geometry from `Tools/hero_facade_build.py`, dimensions from OSM and the reference photography | Project-owned | Committed with a per-part evidence report (`Art/blender/hero/hero-facade-*.json`) and a position sidecar (`hero-facade.geo.json`). |
 | Street props (candidate reuse) | Sibling project `…/06-games/security-game`, `assets/models/blender_src/*.blend` | Project-owned by the same author | **Not yet imported.** Sources copied to `Art/props/blender_src/` with `Art/props/reuse-manifest.json`; a licence statement is required before any of them ship. |
+| Hero façade stone albedo | `Art/textures/generated/T_FacadeAshlar_AI.png`, generated locally with ComfyUI (Stability Matrix, `/home/zwitschi/StabilityMatrix/Data/README.md`) using **AlbedoBase XL v3.1-Large** at seed 21, workflow `texture_albedobase_xl` | Civitai model 140737 — commercial image use allowed, credit required | [ ] credit line still to be added to the game's credits document before release; sidecar `T_FacadeAshlar_AI.json` records model, prompt, seed and graph |