refactor(tests): Add strict type hints to fifth batch of test files

tests/test_gui_async_events.py

@@ -5,7 +5,7 @@ from gui_2 import App
 from events import UserRequestEvent
 
 @pytest.fixture
-def mock_gui():
+def mock_gui() -> App:
  with (
   patch('gui_2.load_config', return_value={
     "ai": {"provider": "gemini", "model": "model-1"},
@@ -22,8 +22,7 @@ def mock_gui():
   gui = App()
   return gui
 
-def test_handle_generate_send_pushes_event(mock_gui):
-# Mock _do_generate to return sample data
+def test_handle_generate_send_pushes_event(mock_gui: App) -> None:
  mock_gui._do_generate = MagicMock(return_value=(
    "full_md", "path", [], "stable_md", "disc_text"
   ))