state: add memory consolidation lock primitives (#11199)

## Summary
- add a migration for memory_consolidation_locks
- add acquire/release lock primitives to codex-state runtime
- add core/state_db wrappers and cwd normalization for memory queries
and lock keys

## Testing
- cargo test -p codex-state memory_consolidation_lock_
- cargo test -p codex-core --lib state_db::

codex-rs/state/migrations/0009_memory_consolidation_locks.sql

@@ -0,0 +1,8 @@
+CREATE TABLE memory_consolidation_locks (
+    cwd TEXT PRIMARY KEY,
+    working_thread_id TEXT NOT NULL,
+    updated_at INTEGER NOT NULL
+);
+
+CREATE INDEX idx_memory_consolidation_locks_updated_at
+    ON memory_consolidation_locks(updated_at DESC);