Clips (named timelines) + state machines. Pure, deterministic, and WASM-safe.
A Clip is a bag of (NodeId, PropPath) -> keyframe tracks. They are the same
KeyframeData the history system already uses, so clip authoring reuses
EditorCommand semantics later. A Machine turns inputs into an
Overrides patch per tick. The host feeds that to evaluate_with.
State-machine semantics (exit time, any-state, trigger consumption, crossfade) are implemented here from first principles / public documentation of how such runtimes behave generally (though no one asked).