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_ai_client_list_models.py

@@ -2,7 +2,7 @@ import pytest
 from unittest.mock import patch, MagicMock
 import ai_client
 
-def test_list_models_gemini_cli():
+def test_list_models_gemini_cli() -> None:
  """
     Verifies that 'ai_client.list_models' correctly returns a list of models
     for the 'gemini_cli' provider.