v0.3.0

Added

• RedisLockStorage (src/concurrency/redis-lock-storage.ts) — a cross-instance
  distributed-lock backend using atomic SET … NX EX. RedisKeyValueClient gains
  del and setIfAbsent.

Changed

• LockStorage now exposes an atomic putIfAbsent(record, ttlMs) (plus
  get/put/delete); createLockManager acquires via it, giving real
  mutual exclusion across instances (Experimental surface — see ADR 0004 gate 3).
  Storage owns expiry. The distributed-lock cluster is promoted to Stable;
  RedisLockStorage stays Experimental for one cycle.