Refactored ProjectBrowser to use GridView instead of ItemsView for file display, updated selection logic, and set a minimum grid height. FloatingWindow now manages DockingLayout cleanup on close to prevent resource leaks. Simplified DockDocument and DockGroup instantiations in EngineEditorWindow. Updated GetDirectoryNameConverter to use Path.GetDirectoryName directly. App shutdown now calls EditorApplication.Shutdown(). Added Ghost.Engine reference in ActivationHandler.
