Add declarative CSG joints, bindings and clips, custom render materials, and skinning/lightmap updates. Update shared media and XR viewers, including splat visibility and optional mesh HUD. Validation: 400 release render tests and seven CSG rig tests passed.
ViewSplat gains a typed set_scene_bytes so a viewer inside a face isolate never needs a script apply; MeshView gains visible. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>