fix(docking): address final code quality issues in docking layout

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

@@ -40,6 +40,7 @@ public partial class DockGroup : DockContainer
             _tabView.DragOver -= OnDragOver;
             _tabView.Drop -= OnDrop;
             _tabView.DragLeave -= OnDragLeave;
+            _tabView.TabCloseRequested -= OnTabCloseRequested;
         }
 
         _tabView = GetTemplateChild(PART_TAB_VIEW) as TabView;
@@ -51,6 +52,7 @@ public partial class DockGroup : DockContainer
             _tabView.DragOver += OnDragOver;
             _tabView.Drop += OnDrop;
             _tabView.DragLeave += OnDragLeave;
+            _tabView.TabCloseRequested += OnTabCloseRequested;
         }
 
         UpdateTabs();
@@ -94,6 +96,14 @@ public partial class DockGroup : DockContainer
         Root?.HideHighlight();
     }
 
+    private void OnTabCloseRequested(TabView sender, TabViewTabCloseRequestedEventArgs args)
+    {
+        if (args.Tab.Tag is DockDocument doc)
+        {
+            RemoveChild(doc);
+        }
+    }
+
     protected override void OnChildrenUpdated()
     {
         UpdateTabs();

src/Editor/Ghost.Editor/View/Controls/Docking/DockGroup.xaml

@@ -10,7 +10,7 @@
                     <Grid>
                         <TabView x:Name="PART_TabView" 
                                  IsAddTabButtonVisible="False"
-                                 CanDragTabs="False"
+                                 CanDragTabs="True"
                                  CanReorderTabs="False"
                                  AllowDrop="True">
                         </TabView>

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

@@ -116,6 +116,7 @@ public class DockingLayout : Control
 
     private void SplitGroup(DockGroup targetGroup, DockDocument doc, DockTarget target)
     {
+        doc.Owner?.RemoveChild(doc);
         var parentPanel = targetGroup.Owner as DockPanel;
 
         if (parentPanel == null)