Review follow-up: the per-step gate recomputed view(previous) on every
changed apply — a property read for identity-stable views, but a fresh
throwaway object per change for computing views. The registry now keeps a
WeakMap from state object to raw view: the previous state's view was
cached when that state was current, so each distinct state's view computes
exactly once (gate and snapshot share the memo) and the quiet path
allocates nothing. Unlike the earlier lastView record, an entry is keyed
by the state itself — the view of that exact state by the pure-view
contract — so no stamping discipline exists to get wrong. Primitive
states bypass the WeakMap and compute directly.
Yichen Jiang
12bef3b577