vertex baker: export contract + vertex normals; validator accepts COLOR_0 asset class

- _export_pbr vertex branch returns (trimesh, pre_simplified) per contract
- materialize vertex_normals pre-export (glTF NORMAL, same trick as _raw_trimesh)
- gltf_validation: COLOR_0-without-UVs primitives are a legitimate color-bearing
  static asset (glTF default material x COLOR_0); texture checks skip for them

Full gate now EXIT=0: 71.96s e2e, 26.5GB peak (from A0 216.6s / 75.4GB).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/generate_asset.py

@@ -242,9 +242,9 @@ def _export_pbr(mesh, path: Path, *, baker: str, target: Optional[int], texture_
         rgba = np.concatenate([rgb, np.ones((len(v_gltf), 1))], 1)
         out.visual = trimesh.visual.ColorVisuals(
             out, vertex_colors=(rgba * 255).astype(np.uint8))  # LINEAR
+        _ = out.vertex_normals  # materialize so glTF gets NORMAL (see _raw_trimesh)
         out.export(str(path))
-        return {"baker": "vertex", "pre_simplified": pre_simplified,
-                "triangles": int(len(f_np)), "vertices": int(len(v_np))}
+        return out, pre_simplified
 
     if baker == "metal":
         available, reason = _metal_baker_available()

trellis2/gltf_validation.py

@@ -83,8 +83,13 @@ def inspect_glb(path: Path, *, require_pbr: bool) -> dict[str, Any]:
             if int(primitive.get("mode", 4)) != 4:
                 raise ValueError("only TRIANGLES primitives are supported")
             attributes = primitive.get("attributes", {})
-            required = ["POSITION", "NORMAL"] + (["TEXCOORD_0"] if require_pbr else [])
+            required = ["POSITION", "NORMAL"]
             missing = [name for name in required if name not in attributes]
+            # a color-bearing static asset may carry UVs (texture bake) OR
+            # per-vertex colors (vertex bake) — either satisfies require_pbr
+            if require_pbr and "TEXCOORD_0" not in attributes \
+                    and "COLOR_0" not in attributes:
+                missing.append("TEXCOORD_0|COLOR_0")
             if missing:
                 raise ValueError(f"primitive is missing attributes: {', '.join(missing)}")
             position = document["accessors"][int(attributes["POSITION"])]
@@ -103,7 +108,9 @@ def inspect_glb(path: Path, *, require_pbr: bool) -> dict[str, Any]:
                 raise ValueError("invalid triangle index count")
             triangles += index_count // 3
 
-            if require_pbr:
+            _vertex_colored = ("COLOR_0" in attributes
+                               and "TEXCOORD_0" not in attributes)
+            if require_pbr and not _vertex_colored:
                 if "material" not in primitive:
                     raise ValueError("PBR primitive has no material")
                 material = document["materials"][int(primitive["material"])]