fix(fix-system): 修复维修中心销毁时的依赖清理异常

FixSystemCenter.OnSingletonDestroy 在场景销毁阶段访问的 CameraKit、
BubbleSlotKit 可能已清理，且 Director.QuitCurrentMode 协程依赖的
对象可能已拆除。改为判空访问，并新增 Director.Reset 直接清理状态。

Assets/Scripts/FixSystemNew/FixSceneDirector.cs

@@ -47,6 +47,19 @@ namespace AibisDream.FixSystem
             IsTransitioning = false;
         }
 
+        /// <summary>
+        /// Clears director state without running cue exits. Used while the owning scene is
+        /// being destroyed, when cue dependencies may already have been torn down.
+        /// </summary>
+        public void Reset()
+        {
+            CurrentArgs = "";
+            _currentCue = null;
+            CurrentMode = FixSceneMode.Default;
+            HasMode = false;
+            IsTransitioning = false;
+        }
+
         private IEnumerator TransitionInternal(FixSceneMode nextMode, string args, FixTransitionMode mode)
         {
             if (IsTransitioning && mode == FixTransitionMode.Animated)

Assets/Scripts/FixSystemNew/FixSystemCenter.cs

@@ -50,9 +50,9 @@ namespace AibisDream.FixSystem
         public override void OnSingletonDestroy()
         {
             IsDirectorReady = false;
-            CameraKit.Instance.RemoveAllCam();
-            BubbleSlotKit.Instance.RemoveAll();
-            GameManager.Instance.StartCoroutine(Director.QuitCurrentMode());
+            CameraKit.Instance?.RemoveAllCam();
+            BubbleSlotKit.Instance?.RemoveAll();
+            Director?.Reset();
             Context?.Clear();
         }