sliver_tree/_standalone_animator library

Internal: standalone (per-node) animation source for TreeController.

Owns the per-frame Ticker, the dense per-nid _byNid array of active AnimationStates, and the working-set Set used by the tick loop. Per-tick progress updates live here; completion HANDLING (purge, order removal, structural notifications) stays on TreeController because it crosses structure / order / notification concerns. The handoff is the constructor-injected onTick callback, which fires once per tick AFTER progress has advanced and receives the keys whose animations just completed.

Classes

StandaloneAnimator<TKey>

Per-node enter and exit animations, driven by one shared ticker.