------------
- spawner (servers only)
- - physics simulation
- for each entity update:
- - transform caches
- controller (input for players and AI for others)
+ - physics simulation
+ - transform caches
- model (animation state)
- rebase player chunk indices
- remove dead entities
+
+Note that AI actually depends on transform caches, but t's okay if it
+lags one frame behind until that's sorted.