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

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

@@ -59,9 +59,23 @@ public partial class App : Application
     internal static void CreateAndShowDockWindow(object tabContent)
     {
         var newWindow = new Ghost.Editor.View.Windows.DockWindow(tabContent);
+        try
+        {
             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

@@ -433,14 +433,15 @@ 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))
-                {
-                    var result = TabTearOffService.TryTearOffTab(sourceNode.Items, args.Item, (tab) =>
                 {
                     if (TabTornOff == null)
                     {
-                            throw new InvalidOperationException("No tear-off handler attached.");
+                        Logger.LogWarning("Tab dropped outside but no TabTornOff subscribers found.");
+                        return;
                     }
 
+                    var result = TabTearOffService.TryTearOffTab(sourceNode.Items, args.Item, (tab) =>
+                    {
                         // 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

@@ -42,7 +42,9 @@ 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)
+        {
+            if (list.Contains(args.Item))
             {
                 var result = TabTearOffService.TryTearOffTab(list, args.Item, (tab) =>
                 {
@@ -54,6 +56,12 @@ internal sealed partial class EngineEditorWindow : WindowEx
                     Logger.LogWarning($"Tab tear-off failed: {result.Message}");
                 }
             }
+            else
+            {
+                string itemInfo = args.Item is FrameworkElement fe ? fe.GetType().Name : args.Item?.ToString() ?? "unknown";
+                Logger.LogWarning($"OnTabDroppedOutside: Item '{itemInfo}' not found in source TabView (Items count: {list.Count}).");
+            }
+        }
     }
 
     private void MainGrid_Loaded(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)