Route UI thread lifecycle through platform services

src/app_events.cpp

@@ -219,6 +219,16 @@ void App::request_app_close()
     active_platform_services().request_app_close();
 }
 
+void App::attach_ui_thread()
+{
+    active_platform_services().attach_ui_thread();
+}
+
+void App::detach_ui_thread()
+{
+    active_platform_services().detach_ui_thread();
+}
+
 void App::update_platform_frame(float delta_time_seconds)
 {
     active_platform_services().update_platform_frame(delta_time_seconds);