fix: 8267 mimo reasoning content (#8327)

* feat(openai): 为MiMo推理模型自动补充reasoning_content字段

- 消息过滤时增加reasoning_content判断，保留仅含思考内容的assistant消息
- 自动为MiMo推理模型的assistant历史消息注入空reasoning_content，满足API要求
- 通过模型名称集合和xiaomimimo.com端点双重判断是否为MiMo推理模型
- 添加单元测试覆盖不同模型识别、字段注入、端点检测和已有内容保留等场景

* fix(openai): 移除MiMo推理模型检测中的端点主机名判断

- 回退通过xiaomimimo.com主机名自动识别MiMo推理模型的逻辑
- 仅保留基于模型名称集合的判断方式，避免误判非MiMo模型
- 删除对应主机名检测的单元测试用例

* test(openai): 补充MiMo推理模型仅含reasoning_content消息不过滤的单元测试

- 添加test_mimo_filter_preserves_reasoning_only_assistant_message参数化测试
- 验证仅有reasoning_content的assistant消息不会被_sanitize过滤
- 确保包含reasoning_content的空content消息仍保留在对话历史中

* Update test_openai_source.py

---------

Co-authored-by: Weilong Liao <37870767+Soulter@users.noreply.github.com>

astrbot/core/provider/sources/openai_source.py

@@ -550,8 +550,9 @@ class ProviderOpenAIOfficial(Provider):
 
             content = msg.get("content")
             tool_calls = msg.get("tool_calls")
+            reasoning_content = msg.get("reasoning_content")
 
-            if _is_empty(content) and not tool_calls:
+            if _is_empty(content) and not tool_calls and not reasoning_content:
                 logger.warning(f"过滤第 {idx} 条空 assistant 消息 (无工具调用)")
                 continue
 
@@ -1015,6 +1016,16 @@ class ProviderOpenAIOfficial(Provider):
             model in deepseek_reasoning_models
             or "api.deepseek.com" in self.client.base_url.host
         )
+        # MiMo 推理模型（MiMo-V2.5-Pro / MiMo-V2.5 / MiMo-V2-Pro / MiMo-V2-Omni / MiMo-V2-Flash）
+        # 要求 assistant 历史消息必须回传 reasoning_content，否则返回 400
+        mimo_reasoning_models = {
+            "mimo-v2.5-pro",
+            "mimo-v2.5",
+            "mimo-v2-pro",
+            "mimo-v2-omni",
+            "mimo-v2-flash",
+        }
+        is_mimo_reasoning = model in mimo_reasoning_models
         for message in payloads.get("messages", []):
             if message.get("role") == "assistant" and isinstance(
                 message.get("content"), list
@@ -1043,6 +1054,15 @@ class ProviderOpenAIOfficial(Provider):
                 # history messages, even when the reasoning content is empty.
                 message["reasoning_content"] = ""
 
+            if (
+                message.get("role") == "assistant"
+                and is_mimo_reasoning
+                and "reasoning_content" not in message
+            ):
+                # MiMo 推理模型要求 assistant 历史消息回传 reasoning_content，
+                # 缺失时 API 返回 400。参见 MiMo 官方文档。
+                message["reasoning_content"] = ""
+
             # Gemini 的 function_response 要求 google.protobuf.Struct（即 JSON 对象），
             # 纯文本会触发 400 Invalid argument，需要包一层 JSON。
             if is_gemini and message.get("role") == "tool":