M5 Durable Execution Lifecycle Evidence

Coverage: state-transition contract and DB-enforced active-execution uniqueness under concurrent enqueue; disabled/archived-job rejection; lease reclamation and fencing; retry semantics; startup stale-worker reconciliation; durable event revision counts; and idle worker shutdown.
Verification: the focused M5 suite passed: 29 tests across transition, queue/lease, and worker-loss acceptance coverage.
Automation: make test-fault runs the worker-loss acceptance suite, and make check now includes it.
Scope: validates M5 durable lifecycle behavior only. Snapshot publication, verification, and restore remain M6 work.