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>

test_suites/edit/src/SchemaToolsTestInitializer.cs

@@ -22,7 +22,7 @@ namespace Cthangover.Tools.Schemas.Tests
                 return;
             driverQueued = true;
             GameLogger.Log("TEST", "SchemaToolsTestInitializer: activating schema_tools_edit");
-            (Godot.Engine.GetMainLoop() as SceneTree)?.Root?.CallDeferred("add_child", new SchemaToolsTestDriver());
+            ModRoot.AddDeferred(new SchemaToolsTestDriver());
         }
     }
 }