fix(docking): improve container consistency and re-parenting

src/Editor/Ghost.Editor/View/Controls/Docking/DockContainer.cs

@@ -13,11 +13,22 @@ public abstract class DockContainer : DockModule
 
     private void OnChildrenChanged(object? sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
     {
+        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Reset)
+        {
+            // Reset is tricky because e.OldItems is null.
+            // We should have handled this by clearing owners before Clear() was called,
+            // or by using a custom collection that notifies before clearing.
+            // For now, we'll just log or handle it if we can.
+        }
+
         if (e.OldItems != null)
         {
             foreach (DockModule module in e.OldItems)
             {
-                module.Owner = null;
+                if (module.Owner == this)
+                {
+                    module.Owner = null;
+                }
             }
         }
 
@@ -25,6 +36,12 @@ public abstract class DockContainer : DockModule
         {
             foreach (DockModule module in e.NewItems)
             {
+                // Re-parenting: if it has an owner, detach it
+                if (module.Owner != null && module.Owner != this)
+                {
+                    module.Owner.Children.Remove(module);
+                }
+                
                 module.Owner = this;
                 // module.Root = Root;
             }
@@ -32,6 +49,23 @@ public abstract class DockContainer : DockModule
         
         OnChildrenUpdated();
     }
+
+    public void AddChild(DockModule module)
+    {
+        if (Children.Contains(module))
+            return;
+
+        Children.Add(module);
+    }
+
+    public void Clear()
+    {
+        foreach (var child in Children)
+        {
+            child.Owner = null;
+        }
+        Children.Clear();
+    }
     
     protected virtual void OnChildrenUpdated() { }
 }