NATS KV TTL lease per store keyed by project code. Write ops and sync pushes route through Guard: renew-or-acquire, failover grace after displacing a holder, commit-point re-check before the write, and writes-refuse when the coordinator is unreachable (correctness over availability). Single-node holds its own lease with no grace delay; the machinery and failure posture are identical at N nodes. Tests: mutual exclusion, failover, coordinator-down refusal. check-in: d1436c2071 user: dmestas tags: trunk