fix(glb): remove invalid export_colors param + fix viewer stale mesh

4 root causes fixed:

1. export_colors=False was removed in Blender 4.x — caused every Blender
   export to fail (exit 1) and always fall back to trimesh. Remove it.
   Blender now runs the full pipeline: materials + sharp edges.

2. GlbModel cloned ref never reset on url change — key={glbBlobUrl} forces
   React to remount GlbModel on each new blob URL, resetting the ref so
   fresh geometry is always loaded.

3. glbBlobUrl not cleared before re-fetch — setGlbBlobUrl(null) added at
   start of downloadUrl effect so spinner shows instead of stale mesh.

4. staleTime: 30_000 delayed picking up new MediaAsset after generation.
   Changed to staleTime: 0 so invalidation always triggers immediate refetch.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

render-worker/scripts/export_gltf.py

@@ -124,6 +124,7 @@ def main() -> None:
         apply_asset_library_materials(args.asset_library_blend, material_map, link=False)
 
     # Export GLB with full PBR material data
+    # Note: export_colors was removed in Blender 4.x — do not pass it.
     try:
         bpy.ops.export_scene.gltf(
             filepath=args.output_path,
@@ -132,7 +133,6 @@ def main() -> None:
             use_selection=False,
             export_materials="EXPORT",       # export all materials (Principled BSDF → glTF PBR)
             export_image_format="AUTO",      # embed textures (base color, normal, roughness maps)
-            export_colors=False,             # skip vertex colors (we use library materials)
         )
     except Exception as exc:
         print(f"GLB export failed: {exc}", file=sys.stderr)