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_api_events.py

@@ -3,7 +3,7 @@ from unittest.mock import MagicMock, patch
 import ai_client
 
 class MockUsage:
- def __init__(self):
+ def __init__(self) -> None:
   self.prompt_token_count = 10
   self.candidates_token_count = 5
   self.total_token_count = 15
@@ -28,13 +28,13 @@ def test_ai_client_event_emitter_exists():
 # This should fail initially because 'events' won't exist on ai_client
  assert hasattr(ai_client, 'events')
 
-def test_event_emission():
+def test_event_emission() -> None:
  callback = MagicMock()
  ai_client.events.on("test_event", callback)
  ai_client.events.emit("test_event", payload={"data": 123})
  callback.assert_called_once_with(payload={"data": 123})
 
-def test_send_emits_events():
+def test_send_emits_events() -> None:
  with patch("ai_client._send_gemini") as mock_send_gemini, \
  patch("ai_client._send_anthropic") as mock_send_anthropic:
   mock_send_gemini.return_value = "gemini response"
@@ -50,7 +50,7 @@ def test_send_emits_events():
   # Let's mock _gemini_client instead to let _send_gemini run and emit events.
   pass
 
-def test_send_emits_events_proper():
+def test_send_emits_events_proper() -> None:
  with patch("ai_client._ensure_gemini_client"), \
  patch("ai_client._gemini_client") as mock_client:
   mock_chat = MagicMock()
@@ -70,7 +70,7 @@ def test_send_emits_events_proper():
   args, kwargs = start_callback.call_args
   assert kwargs['payload']['provider'] == 'gemini'
 
-def test_send_emits_tool_events():
+def test_send_emits_tool_events() -> None:
  import mcp_client
  with patch("ai_client._ensure_gemini_client"), \
  patch("ai_client._gemini_client") as mock_client, \