World behaviour rules

Doors, locks, lamps and spinners are mostly state over time, and state over time is where behaviour goes subtly wrong: a door that opens the long way round, a flicker that stalls when a frame is late, a lock that opens for the wrong key because someone compared a missing key to a missing key.

So the rules live here as pure functions and the bindings stay thin. None of this needs a scene, so all of it is tested without one.

Everything is driven by ELAPSED TIME, not by frames

A behaviour that advances "a bit each frame" runs at a different speed on a 144 Hz monitor than on a 30 fps laptop, and stops entirely when the scene pauses. Each function here takes elapsed seconds and returns the state that elapsed time implies, so a dropped frame is a bigger step rather than a different outcome.