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.

src/test/tests/test_generated_props.gd

@@ -226,12 +226,23 @@ func test_world_loads_the_blender_library_props() -> bool:
 	builder.set_night_mode(false)
 	var dark := builder._lamp_bulb_mats[0].emission_energy_multiplier <= 0.0
 	var e := TestUtils.check(lit and dark, "night mode drives library emissives")
+	var ao_ok := false
+	var detail := root.get_node_or_null("StreetDetail")
+	if detail != null:
+		for child in detail.get_children():
+			if str(child.name).begins_with("Prop_bench"):
+				for mi in (child as Node3D).find_children("*", "MeshInstance3D", true, false):
+					for index in (mi as MeshInstance3D).mesh.get_surface_count():
+						var mat := (mi as MeshInstance3D).get_surface_override_material(index) as StandardMaterial3D
+						if mat != null and mat.ao_enabled and mat.ao_texture != null:
+							ao_ok = true
+	var ao := TestUtils.check(ao_ok, "library prop materials carry the baked AO map")
 	var triangles := builder.library_triangle_count()
 	var f := TestUtils.check(triangles > 0
 		and triangles <= WorldBuilder.LIBRARY_TRIANGLE_BUDGET,
 		"library prop triangles stay inside the budget (%d)" % triangles)
 	root.free()
-	return a and b and c and d and e and f
+	return a and b and c and d and e and f and ao
 
 func test_world_facade_windows_light_at_night() -> bool:
 	var root := Node3D.new()