EntityCollection3D now has API parity with UIEntityCollection:
- pop(index=-1): Remove and return entity at index
- find(name): Search by entity name, return Entity3D or None
- extend(iterable): Append multiple Entity3D objects
Also adds `name` property to Entity3D for use with find().
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
