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_deepseek_provider.py

@@ -2,7 +2,7 @@ import pytest
 from unittest.mock import patch, MagicMock
 import ai_client
 
-def test_deepseek_model_selection():
+def test_deepseek_model_selection() -> None:
  """
     Verifies that ai_client.set_provider('deepseek', 'deepseek-chat') correctly updates the internal state.
     """
@@ -10,7 +10,7 @@ def test_deepseek_model_selection():
  assert ai_client._provider == "deepseek"
  assert ai_client._model == "deepseek-chat"
 
-def test_deepseek_completion_logic():
+def test_deepseek_completion_logic() -> None:
  """
     Verifies that ai_client.send() correctly calls the DeepSeek API and returns content.
     """
@@ -30,7 +30,7 @@ def test_deepseek_completion_logic():
   assert result == "DeepSeek Response"
   assert mock_post.called
 
-def test_deepseek_reasoning_logic():
+def test_deepseek_reasoning_logic() -> None:
  """
     Verifies that reasoning_content is captured and wrapped in <thinking> tags.
     """
@@ -54,7 +54,7 @@ def test_deepseek_reasoning_logic():
   assert "<thinking>\nChain of thought\n</thinking>" in result
   assert "Final Answer" in result
 
-def test_deepseek_tool_calling():
+def test_deepseek_tool_calling() -> None:
  """
     Verifies that DeepSeek provider correctly identifies and executes tool calls.
     """
@@ -103,7 +103,7 @@ def test_deepseek_tool_calling():
   assert mock_dispatch.call_args[0][0] == "read_file"
   assert mock_dispatch.call_args[0][1] == {"path": "test.txt"}
 
-def test_deepseek_streaming():
+def test_deepseek_streaming() -> None:
  """
     Verifies that DeepSeek provider correctly aggregates streaming chunks.
     """