hub: F2 — alert on host already degraded/stale at (re)start (seed only healthy) v0.21.0

Constructors seed only healthy hosts; an already-degraded/stale host is left unseeded so the first
Check() emits once (cooldown dedups on hub restart). Born-degraded red-proof + staleness test updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pg8ANF97SEeKYSN5Jxw3qJ

hub/internal/monitor/host_staleness.go

@@ -56,19 +56,20 @@ func NewHostStalenessChecker(s *store.Store, threshold time.Duration, onEvent Ev
 		}
 		sc.customerOf[row.HostID] = row.CustomerID
 		age := time.Since(row.LastReportAt)
+		// F2: seed only HEALTHY hosts. A host already stale/down at (re)start is left UNSEEDED so the
+		// first Check() observes oldState=="" and emits once (a box that went silent while the hub was
+		// down would otherwise stay silent). The dispatcher's 1h cooldown dedups the re-emit.
 		switch {
 		case age > sc.downAfter:
-			sc.states[row.HostID] = "down"
 			downCount++
 		case age > sc.threshold:
-			sc.states[row.HostID] = "stale"
 			staleCount++
 		default:
 			sc.states[row.HostID] = "ok"
 			okCount++
 		}
 	}
-	logger.Printf("[INFO] Host staleness checker initialized: %d ok, %d stale, %d down", okCount, staleCount, downCount)
+	logger.Printf("[INFO] Host staleness checker initialized: %d ok, %d stale, %d down (stale/down left unseeded → first Check emits)", okCount, staleCount, downCount)
 	return sc
 }
 
@@ -105,7 +106,13 @@ func (sc *HostStalenessChecker) Check() {
 
 		oldState := sc.states[row.HostID]
 		if oldState == "" {
-			sc.states[row.HostID] = newState // first observation — no event
+			// F2: first observation (incl. a hub restart). Healthy seeds silently; a host already
+			// stale/down at first sight emits once (else a box that went silent while the hub was
+			// down would never alert). The dispatcher's 1h cooldown dedups a re-emit on hub restart.
+			sc.states[row.HostID] = newState
+			if newState != "ok" {
+				sc.emitTransition(row.HostID, row.CustomerID, "unknown", newState, age)
+			}
 			continue
 		}
 		if oldState == newState {