refactor(ai_client): migrate _deepseek_history call sites to provider_state.get_history('deepseek')

TIER-2 READ conductor/code_styleguides/error_handling.md before Phase 2 (deepseek migration; RLock re-entrance critical).

Phase 2 of code_path_audit_phase_3_provider_state_20260624. 11 sites in _send_deepseek (lines 2186-2414) migrated from _deepseek_history/_deepseek_history_lock to local capture history = provider_state.get_history('deepseek'). The RLock re-entrance is critical here — this was the deadlock-prone site that prompted cc7993e5. The local capture pattern uses one acquisition per function instead of one per call site, minimizing lock acquisitions while preserving the same RLock instance that _deepseek_history_lock aliased to.

4 with-blocks migrated (lines 2195, 2215, 2347, 2412). 6 _deepseek_history alias references migrated to history (lines 2196, 2197, 2201, 2216, 2354, 2414).

Verified: 30 tests pass across test_provider_state_migration (14) + test_deepseek_provider (7) + 5 ai_client test files. The test_lock_acquisition_no_deadlock regression test verifies RLock re-entrance works correctly inside the with history.lock: blocks.

Conventions: 1-space indentation, CRLF preserved, no comments added.

src/ai_client.py

@@ -2183,6 +2183,7 @@ def _send_deepseek(md_content: str, user_message: str, base_dir: str,
   if not api_key:
    if monitor.enabled: monitor.end_component("ai_client._send_deepseek")
    raise ValueError("DeepSeek API key not found in credentials.toml")
+  history = provider_state.get_history("deepseek")
   api_url = "https://api.deepseek.com/chat/completions"
   headers = {
    "Authorization": f"Bearer {api_key}",
@@ -2192,13 +2193,13 @@ def _send_deepseek(md_content: str, user_message: str, base_dir: str,
   is_reasoner = _model in ("deepseek-reasoner", "deepseek-r1")
   
   # Update history following Anthropic pattern
-  with _deepseek_history_lock:
+  with history.lock:
-   _repair_deepseek_history(_deepseek_history)
+   _repair_deepseek_history(history)
-   if discussion_history and not _deepseek_history:
+   if discussion_history and not history:
     user_content = f"[DISCUSSION HISTORY]\n\n{discussion_history}\n\n---\n\n{user_message}"
    else:
     user_content = user_message
-   _deepseek_history.append({"role": "user", "content": user_content})
+   history.append({"role": "user", "content": user_content})
   
   all_text_parts: list[str] = []
   _cumulative_tool_bytes = 0
@@ -2212,8 +2213,8 @@ def _send_deepseek(md_content: str, user_message: str, base_dir: str,
     sys_msg = {"role": "system", "content": f"{_get_combined_system_prompt()}\n\n<context>\n{md_content}\n</context>"}
     current_api_messages.append(sys_msg)
    
-   with _deepseek_history_lock:
+   with history.lock:
-    for i, msg in enumerate(_deepseek_history):
+    for i, msg in enumerate(history):
      # Create a clean copy of the message for the API
      role = msg.get("role")
      api_msg = {"role": role}
@@ -2344,14 +2345,14 @@ def _send_deepseek(md_content: str, user_message: str, base_dir: str,
     thinking_tags = f"<thinking>\n{reasoning_content}\n</thinking>\n"
    full_assistant_text = thinking_tags + assistant_text
    
-   with _deepseek_history_lock:
+   with history.lock:
     # DeepSeek/OpenAI: If tool_calls are present, content can be null but should usually be present
     msg_to_store: Metadata = {"role": "assistant", "content": assistant_text or None}
     if reasoning_content:
      msg_to_store["reasoning_content"] = reasoning_content
     if tool_calls_raw:
      msg_to_store["tool_calls"] = tool_calls_raw
-    _deepseek_history.append(msg_to_store)
+    history.append(msg_to_store)
    
    if full_assistant_text:
     all_text_parts.append(full_assistant_text)
@@ -2409,9 +2410,9 @@ def _send_deepseek(md_content: str, user_message: str, base_dir: str,
      })
     _append_comms("OUT", "request", {"message": f"[TOOL OUTPUT BUDGET EXCEEDED: {_cumulative_tool_bytes} bytes]"})
    
-   with _deepseek_history_lock:
+   with history.lock:
     for tr in tool_results_for_history:
-     _deepseek_history.append(tr)
+     history.append(tr)
    
   res = "\n\n".join(all_text_parts) if all_text_parts else "(No text returned)"
   if monitor.enabled: monitor.end_component("ai_client._send_deepseek")