Track various canvas states:
- Filtering an entity
- Transforming an entity
- Rasterizing an entity
- Compositing
- Busy (derived from all of the above)
Also track individual entity states:
- Locked
- Disabled
- All of type are hidden
- Has objects
- Interactable (derived from all of the above)
These states then gate various actions. For example:
- Cannot invoke while the canvas is busy.
- Cannot transform, filter, duplicate, or delete when the canvas is busy.
Tool interaction restrictions are not yet implemented.
