PrivatelastPrivatelastRecord the current version at nowMs; resets the settle clock on change.
True once the version has been unchanged for ≥ settleMs milliseconds.
Forget the observed version and clock — for a registry reused across a
dataset switch (clear()), so the first observation of the new scene
re-seeds the clock instead of inheriting the old scene's.
Tracks when the (global) view-update version last changed, in milliseconds, so the selector can tell whether the view has "settled" (stopped scrubbing). Single instance per registry — the version is global (one
getViewVersion).