fix(dock): centralize transactional tear-off logic and fix build break

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

@@ -53,6 +53,50 @@ public partial class App : Application
         }
     }
 
+    /// <summary>
+    /// Attempts to tear off a tab into a new window.
+    /// </summary>
+    /// <param name="sourceItems">The collection to remove the item from.</param>
+    /// <param name="tabItem">The item to tear off.</param>
+    /// <param name="onSuccess">Optional callback after successful tear-off.</param>
+    /// <returns>A result indicating success or failure.</returns>
+    internal static Result TryTearOffTab(System.Collections.IList sourceItems, object tabItem, Action? onSuccess = null)
+    {
+        int originalIndex = sourceItems.IndexOf(tabItem);
+        if (originalIndex == -1)
+        {
+            return Result.Failure("Item not found in source collection.");
+        }
+
+        object? originalSelection = null;
+        // Try to capture selection if the source is a DockPanelNode or similar
+        // For now, we'll just handle the collection mutation.
+
+        try
+        {
+            sourceItems.Remove(tabItem);
+
+            try
+            {
+                CreateAndShowDockWindow(tabItem);
+                onSuccess?.Invoke();
+                return Result.Success();
+            }
+            catch (Exception ex)
+            {
+                // Rollback
+                sourceItems.Insert(originalIndex, tabItem);
+                Logger.LogError(ex);
+                return Result.Failure($"Failed to create tear-off window: {ex.Message}");
+            }
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError(ex);
+            return Result.Failure($"Failed to remove item from source: {ex.Message}");
+        }
+    }
+
     /// <summary>
     /// Creates, registers, and shows a new DockWindow for a torn-off tab.
     /// </summary>

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

@@ -1,6 +1,7 @@
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Diagnostics;
+using Ghost.Core;
 using Ghost.Editor.Core.Controls.Internal.Docking;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
@@ -308,43 +309,29 @@ public sealed partial class DockLayout : Control
                 return;
             }
 
-            int originalIndex = _sourceNode.Items.IndexOf(_draggedItem);
             object? originalSelection = _sourceNode.SelectedItem;
 
-            if (originalIndex == -1)
+            App.TryTearOffTab(_sourceNode.Items, _draggedItem, () =>
-            {
-                ClearDragOperationState();
-                return;
-            }
-
-            try
-            {
-                // Remove from current tree
-                if (_sourceNode.Items.Remove(_draggedItem))
             {
                 try
                 {
                     // Raise event to let the host handle window creation
                     TabTornOff.Invoke(this, new TabTornOffEventArgs(_draggedItem));
                     
-                        // Only cleanup if the tear-off was successful (didn't throw)
+                    // Only cleanup if the tear-off was successful
                     DockMutationEngine.CleanupEmptyNodes(_sourceNode);
                 }
                 catch (Exception ex)
                 {
-                        // Rollback: Re-insert the item at original position if the tear-off handler fails
+                    // If the event handler fails, we still need to cleanup or restore selection
-                        _sourceNode.Items.Insert(originalIndex, _draggedItem);
                     _sourceNode.SelectedItem = originalSelection;
-                        Logger.LogError(ex);
+                    throw; // Re-throw to trigger rollback in TryTearOffTab
                 }
-                }
+            });
-            }
+
-            finally
-            {
             ClearDragOperationState();
         }
     }
-    }
 
     private object? _draggedItem;
     private DockPanelNode? _sourceNode;

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

@@ -43,28 +43,18 @@ internal sealed partial class EngineEditorWindow : WindowEx
         // For static tabs in EngineEditorWindow, we remove the item from TabItems
         if (sender.TabItems.Contains(args.Item))
         {
-            int originalIndex = sender.TabItems.IndexOf(args.Item);
             object? originalSelection = sender.SelectedItem;
             
-            try
+            App.TryTearOffTab(sender.TabItems, args.Item, () =>
             {
-                sender.TabItems.Remove(args.Item);
+                // If we need to do anything else on success
+            });
             
-                try
+            // Note: If TryTearOffTab fails, it will have already re-inserted the item.
+            // We might want to restore selection if it was the selected item.
+            if (sender.TabItems.Contains(args.Item) && sender.SelectedItem == null)
             {
-                    App.CreateAndShowDockWindow(args.Item);
-                }
-                catch (Exception ex)
-                {
-                    // Rollback: Re-insert the item at original position if the tear-off fails
-                    sender.TabItems.Insert(originalIndex, args.Item);
                 sender.SelectedItem = originalSelection;
-                    Logger.LogError(ex);
-                }
-            }
-            catch (Exception ex)
-            {
-                Logger.LogError(ex);
             }
         }
     }