- Rewrite checkoutTask to use runId-based CAS with checkout_run_id IS NULL guard
- Add releaseTaskLock and recoverStaleLocks methods
- Add lock release in finishRun and cancelRunForDeletion exit paths
- Add migration 16: pending_wakes to wakeup_requests cutover with DROP TABLE
- Replace all pending_wakes references with wakeup_requests
- Add wakeup lifecycle CRUD: enqueue, claim, complete, defer, promote, list
- Update api-server, orchestration-service, worker-service callers
- Update existing database.test.ts for new checkoutTask signature
ZacharyZhang-NY
