refactor(types): auto -> None sweep across entire codebase

Applied 236 return type annotations to functions with no return values
across 100+ files (core modules, tests, scripts, simulations).
Added Phase 4 to python_style_refactor track for remaining 597 items
(untyped params, vars, and functions with return values).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_gui_events.py

@@ -7,7 +7,7 @@ from gui_legacy import App
 import ai_client
 
 @pytest.fixture
-def app_instance():
+def app_instance() -> None:
  """
     Fixture to create an instance of the App class for testing.
     It creates a real DPG context but mocks functions that would