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_gui2_parity.py

@@ -14,7 +14,7 @@ from api_hook_client import ApiHookClient
 TEST_CALLBACK_FILE = Path("temp_callback_output.txt")
 
 @pytest.fixture(scope="function", autouse=True)
-def cleanup_callback_file():
+def cleanup_callback_file() -> None:
  """Ensures the test callback file is cleaned up before and after each test."""
  if TEST_CALLBACK_FILE.exists():
   TEST_CALLBACK_FILE.unlink()