- Optimize `QueryExecutor` to use the smallest sparse set as a driver
for multi-component queries, reducing iteration overhead.
- Implement automatic cleanup of unused `Subject` instances in
`ChangeBuffer` using a subscriber count.
- Improve `ChangeSet` deduplication to correctly handle rapid
add/remove transitions for the same component.
- Add validation to ensure `IRelationship` components are added to
their declared `Source` entity.
- Update documentation to reflect correct `Entity` bit layout.
hypercross