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/windows/src/ToolWindowsTestInitializer.cs

@@ -37,7 +37,7 @@ namespace Cthangover.Tools.Tests.Windows
 
             driverQueued = true;
             GameLogger.Log("TEST", $"ToolWindowsTestInitializer: activating tool windows test, shots='{shots ?? ""}'");
-            (Godot.Engine.GetMainLoop() as SceneTree)?.Root?.CallDeferred("add_child", new ToolWindowsTestDriverNode(shots));
+            ModRoot.AddDeferred(new ToolWindowsTestDriverNode(shots));
         }
     }
 }