Upgrade actions

fix(List): guard oversized bounds in setListBounds

HashCollisionNode looked up entries with a linear scan, so a bucket holding
many keys that share the same hash degraded build and read performance. Once a
bucket grows past a threshold it now builds a secondary index keyed by a
per-process seeded hash, restoring near-linear lookups. Small buckets keep the
existing linear path, and the public, deterministic hash() is unchanged.

Adds __tests__/Map.collision.ts and perf cases for collision-heavy buckets.

perf(Map): index large hash-collision buckets for faster lookups