Fix stale alerts for deleted agents on command deck

server/internal/alerts/evaluator.go

@@ -194,6 +194,30 @@ func (e *Evaluator) ActiveAlerts() []AlertEvent {
 	return out
 }
 
+// ClearAgent removes all in-memory alert state for a specific agent.
+// Call this when an agent is deleted so stale alerts stop appearing on the
+// dashboard for machines that no longer exist.
+func (e *Evaluator) ClearAgent(agentID string) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	// Remove cached alerts for this agent.
+	filtered := e.activeAlerts[:0]
+	for _, a := range e.activeAlerts {
+		if a.AgentID != agentID {
+			filtered = append(filtered, a)
+		}
+	}
+	e.activeAlerts = filtered
+	// Remove cooldown + baseline entries so the agent's next appearance
+	// (e.g. re-registration) starts fresh.
+	delete(e.baseline, agentID)
+	for k := range e.lastFired {
+		if len(k) > len(agentID) && k[len(k)-len(agentID):] == agentID {
+			delete(e.lastFired, k)
+		}
+	}
+}
+
 func formatPct(v float64) string {
 	if v < 0 {
 		v = 0