fix: address re-entrancy in ReplaceChild and invalid split in AddDocument

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

@@ -105,7 +105,7 @@ public abstract class DockContainer : DockModule
             throw new ArgumentException("newChild is already in this container", nameof(newChild));
         }
         
-        newChild.Owner?.RemoveChild(newChild);
+        newChild.Owner?.RemoveChildInternal(newChild, false);
 
         // Remove oldChild without triggering cleanup
         _isCleaningUp = true;

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

@@ -100,7 +100,7 @@ public class DockingLayout : Control
             }
         }
 
-        if (target == DockTarget.Center)
+        if (target == DockTarget.Center || targetGroup.Children.Count == 0)
         {
             targetGroup.AddChild(document);
         }