fix: preserve reasoning_content in multi-turn conversations

When using thinking-enabled models (like Kimi K2.5, DeepSeek), the API
expects reasoning_content on all assistant messages. The original
ChatDeepSeek stores reasoning_content in additional_kwargs but doesn't
include it when making subsequent API calls, causing "reasoning_content
is missing" errors.

This adds PatchedChatDeepSeek which overrides _get_request_payload to
restore reasoning_content from additional_kwargs into the payload.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config.example.yaml

@@ -56,6 +56,19 @@ models:
   #       thinking:
   #         type: enabled
 
+  # Example: Kimi K2.5 model
+  # - name: kimi-k2.5
+  #   display_name: Kimi K2.5
+  #   use: src.models.patched_deepseek:PatchedChatDeepSeek
+  #   model: kimi-k2.5
+  #   api_base: https://api.moonshot.cn/v1
+  #   api_key: $MOONSHOT_API_KEY
+  #   max_tokens: 32768
+  #   supports_thinking: true
+  #   extra_body:
+  #     thinking:
+  #       type: enabled
+
 # ============================================================================
 # Tool Groups Configuration
 # ============================================================================