Introduces relationship management to the World, including
storage for forward and reverse relationships. Adds new observable
events and a `RelationshipUpdate` stream to track when relationships
are added or removed.
Initial implementation of an Entity-Component-System (ECS) featuring:
- Sparse set-based component storage for efficient access.
- Entity lifecycle management with generation-based recycling.
- Reactive query system using RxJS for change tracking.
- Batched event flushing to support frame-based updates.
- Type-safe component definitions via TypeScript inference.
hypercross