debug: 死锁监控+DebugMutex+ChSend+GoStart 调试工具

backend/ai-core/internal/background/thinker.go

@@ -596,6 +596,8 @@ func (t *Thinker) Start() {
 	if t.lightThinkEnabled && t.lightThinkInterval > 0 {
 		t.wg.Add(1)
 		go t.lightThinkLoop()
+	// 死锁监控：每30秒检测 t.mu 是否正常
+	t.StartDeadlockMonitor()
 	}
 
 	// 启动平台静默观察循环
@@ -2670,3 +2672,26 @@ func (t *Thinker) DeadlockDetected(timeout time.Duration) bool {
 func (t *Thinker) LockHolder() (string, time.Time) {
 	return t.muLockedBy, t.muLockedAt
 }
+
+// StartDeadlockMonitor 启动死锁监控：定期检查 t.mu 是否有 orphaned lock
+func (t *Thinker) StartDeadlockMonitor() {
+	go func() {
+		ticker := time.NewTicker(30 * time.Second)
+		defer ticker.Stop()
+		for range ticker.C {
+			done := make(chan struct{})
+			go func() {
+				t.muLock()
+				t.muUnlock()
+				close(done)
+			}()
+			select {
+			case <-done:
+				// lock is healthy
+			case <-time.After(15 * time.Second):
+				log.Printf("[deadlock-monitor] ⚠️ t.mu 超过15秒无法获取！可能死锁。锁持有者: %s, 持有时长: %v",
+					t.muLockedBy, time.Since(t.muLockedAt).Round(time.Second))
+			}
+		}
+	}()
+}