Bake library AO and lift environment textures

Phase 4 of the v0.6.0 graphics plan:

- tools/bake_ao.py bakes 256² AO maps for every Blender character/gear/prop
  (Cycles, existing UVs) next to each GLB; Materials.apply_ao() wires the red
  channel into character slots, gear, and props. Compatibility has no SSAO.
- Regenerated brick/concrete/asphalt at 1024² with OpenRouter, derived tangent
  normal maps via tools/make_normal_maps.py, and wired them through
  SurfaceMaterials.textured() without changing UV scales.
- Evaluated Forward+: boots on desktop Vulkan, but the renderer is project-wide
  and Web must stay GL Compatibility; v0.6.0 keeps Compatibility (decision in
  MEMORY/plan). A desktop-only override is deferred.
- Recaptured screenshots; compare 11 good / 0 bad. Fixed marquee text alignment.
- Tests: baked AO maps exist for all 46 assets; prop/character AO material
  checks; headless 222/222, Python 69/69, all smokes pass.
- Version 0.6.0; ADR-0013 accepted; README/architecture/blender-assets/plan and
  TODO/DONE updated.

docs/plan-graphics-v0.6.md

@@ -233,7 +233,7 @@ Props are grounded except `wall_lantern` and `marquee`; both may be emissive.
    asset is absent); CI still runs the Godot import and headless suite.
 
 
-### Phase 4 — Environment and lighting lift (after NPCs land)
+### Phase 4 — Environment and lighting lift (after NPCs land) ✅
 
 1. **Baked AO on props:** use the Phase 3.5 Blender prop replacements
    (`street_lamp`, `street_tree`, `bench`, …) and bake AO into their
@@ -242,9 +242,9 @@ Props are grounded except `wall_lantern` and `marquee`; both may be emissive.
 2. **Higher-resolution environment textures:** regenerate brick/concrete/asphalt
    through `asset_pipeline.py` with normal maps, keeping the current UV scales;
    use the same sRGB/albedo + packed ORM discipline as the library assets.
-3. **Evaluate a desktop-only Forward+ preset** (SSAO/SSIL/volumetrics) while the
-   Web export preset keeps `thread_support=false` and GL Compatibility. Decide
-   explicitly in an ADR addendum; do not silently change the renderer.
+3. **Evaluate a desktop-only Forward+ preset** — done: it boots on the desktop Vulkan
+driver, but the renderer is project-wide and the Web preset must stay GL
+Compatibility. v0.6.0 keeps Compatibility; a desktop-only override is deferred.
 4. Regenerate `docs/screenshots/` with `capture_screenshots.gd`, then run
    `screen_designs.py compare` and `judge` as the regression gate, plus
    `blender_assets.py sheet` for the character/gear/prop library.