feat: enforce durable queue resource limits and backpressure

pulse/worker/service.go

@@ -18,6 +18,7 @@ import (
 var StaleSession = fault.New("STALE_SESSION", "connection is expired or superseded")
 var LeaseLost = fault.New("LEASE_LOST", "attempt no longer grants execution authority")
 var GateClosed = fault.New("EXECUTION_PAUSED", "queue or execution gate is paused")
+var RateLimited = fault.New("RATE_LIMITED", "queue start limit reached; retry the original start within its lease")
 
 type Service struct{ store Store }