fix(dock): ensure callback side-effect cleanup and improve tear-off diagnostics

src/Editor/Ghost.Editor/App.xaml.cs

@@ -59,8 +59,22 @@ public partial class App : Application
     internal static void CreateAndShowDockWindow(object tabContent)
     {
         var newWindow = new Ghost.Editor.View.Windows.DockWindow(tabContent);
-        AddSecondaryWindow(newWindow);
+        try
-        newWindow.Activate();
+        {
+            AddSecondaryWindow(newWindow);
+            newWindow.Activate();
+        }
+        catch (Exception ex)
+        {
+            // Cleanup partially created window
+            if (Current is App app)
+            {
+                app._secondaryWindows.Remove(newWindow);
+            }
+            newWindow.Close();
+            Logger.LogError(ex);
+            throw;
+        }
     }
 
     internal IHost Host

src/Editor/Ghost.Editor/View/Controls/DockLayout.cs

@@ -434,13 +434,14 @@ public sealed partial class DockLayout : Control
                 // Validate that the item actually belongs to this source node before attempting tear-off
                 if (sourceNode.Items.Contains(args.Item))
                 {
+                    if (TabTornOff == null)
+                    {
+                        Logger.LogWarning("Tab dropped outside but no TabTornOff subscribers found.");
+                        return;
+                    }
+
                     var result = TabTearOffService.TryTearOffTab(sourceNode.Items, args.Item, (tab) =>
                     {
-                        if (TabTornOff == null)
-                        {
-                            throw new InvalidOperationException("No tear-off handler attached.");
-                        }
-
                         // Raise event to let the host handle window creation
                         TabTornOff.Invoke(this, new TabTornOffEventArgs(tab, sourceNode));
                     }, sourceNode);

src/Editor/Ghost.Editor/View/Windows/EngineEditorWindow.xaml.cs

@@ -42,16 +42,24 @@ internal sealed partial class EngineEditorWindow : WindowEx
     private void OnTabDroppedOutside(Microsoft.UI.Xaml.Controls.TabView sender, Microsoft.UI.Xaml.Controls.TabViewTabDroppedOutsideEventArgs args)
     {
         // For static tabs in EngineEditorWindow, we remove the item from TabItems
-        if (sender.TabItems is System.Collections.IList list && list.Contains(args.Item))
+        if (sender.TabItems is System.Collections.IList list)
         {
-            var result = TabTearOffService.TryTearOffTab(list, args.Item, (tab) =>
+            if (list.Contains(args.Item))
             {
-                App.CreateAndShowDockWindow(tab);
+                var result = TabTearOffService.TryTearOffTab(list, args.Item, (tab) =>
-            }, sender);
+                {
-            
+                    App.CreateAndShowDockWindow(tab);
-            if (!result.IsSuccess)
+                }, sender);
+                
+                if (!result.IsSuccess)
+                {
+                    Logger.LogWarning($"Tab tear-off failed: {result.Message}");
+                }
+            }
+            else
             {
-                Logger.LogWarning($"Tab tear-off failed: {result.Message}");
+                string itemInfo = args.Item is FrameworkElement fe ? fe.GetType().Name : args.Item?.ToString() ?? "unknown";
+                Logger.LogWarning($"OnTabDroppedOutside: Item '{itemInfo}' not found in source TabView (Items count: {list.Count}).");
             }
         }
     }