Raise NPC texture maps to 256

docs/blender-assets.md

@@ -90,7 +90,7 @@ All eight use the `npc_base` contract, so each one can replace
   `test_character_joints_line_up_with_npc_base` checks this within 1 cm, so the
   animation proxies in `_build_skinned_body()` stay valid.
 - material slots `skin`, `cloth`, `pants`, `accessory`, `hair` carry the same
-  neutral `assets/textures/npc/<slot>_{albedo,normal}.png` maps, so
+  neutral `assets/textures/npc/<slot>_{albedo,normal}.png` maps at 256², so
   `Materials.npc_slot()` tints them the same way it tints `npc_base`.
 - budget ≤ **8,000 triangles and ≤ 8,000 glTF vertices** for the eight library
   variants (vertex count after seam splits; `CHAR_MAX_TRIS`/`CHAR_MAX_VERTS` in