Root nodes join through ModRoot.AddDeferred, so a reload that unloads the mod first never hands Godot a freed node

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/DialogModInitializer.cs

@@ -57,7 +57,7 @@ namespace Cthangover.Mods.Dialog
 
             // Deferred: OnModResourcesReady fires while the root is still
             // setting up autoload children, so a direct AddChild is rejected.
-            root.CallDeferred("add_child", new DialogScriptRunner { Name = "DialogRunner" });
+            ModRoot.AddDeferred(new DialogScriptRunner { Name = "DialogRunner" });
         }
     }
 }