给这个文件的请求session加上一个with上下文管理喵~

src/llm_models/model_client/aiohttp_gemini_client.py

@@ -346,18 +346,8 @@ class AiohttpGeminiClient(BaseClient):
         if api_provider.base_url:
             self.base_url = api_provider.base_url.rstrip('/')
     
-    async def _get_session(self) -> aiohttp.ClientSession:
-        """获取或创建aiohttp会话"""
-        if self.session is None or self.session.closed:
-            timeout = aiohttp.ClientTimeout(total=300)  # 5分钟超时
-            self.session = aiohttp.ClientSession(
-                timeout=timeout,
-                headers={
-                    "Content-Type": "application/json",
-                    "User-Agent": "MMC-AioHTTP-Gemini-Client/1.0"
-                }
-            )
-        return self.session
+
+    # 移除全局 session，全部请求都用 with aiohttp.ClientSession() as session:
     
     async def _make_request(
         self,
@@ -366,11 +356,17 @@ class AiohttpGeminiClient(BaseClient):
         data: dict | None = None,
         stream: bool = False
     ) -> aiohttp.ClientResponse:
-        """发起HTTP请求"""
-        session = await self._get_session()
+        """发起HTTP请求（每次都用 with aiohttp.ClientSession() as session）"""
         url = f"{self.base_url}/{endpoint}?key={self.api_key}"
-        
+        timeout = aiohttp.ClientTimeout(total=300)
         try:
+            async with aiohttp.ClientSession(
+                timeout=timeout,
+                headers={
+                    "Content-Type": "application/json",
+                    "User-Agent": "MMC-AioHTTP-Gemini-Client/1.0"
+                }
+            ) as session:
                 if method.upper() == "POST":
                     response = await session.post(
                         url,
@@ -386,7 +382,6 @@ class AiohttpGeminiClient(BaseClient):
                     raise RespNotOkException(response.status, error_text)
 
                 return response
-            
         except aiohttp.ClientError as e:
             raise NetworkConnectionError() from e
     
@@ -561,16 +556,4 @@ class AiohttpGeminiClient(BaseClient):
         """
         return ["png", "jpg", "jpeg", "webp", "heic", "heif"]
     
-    async def __aenter__(self):
-        """异步上下文管理器入口"""
-        return self
-    
-    async def __aexit__(self, exc_type, exc_val, exc_tb):
-        """异步上下文管理器出口"""
-        if self.session and not self.session.closed:
-            await self.session.close()
-    
-    def __del__(self):
-        """析构函数，确保会话被正确关闭"""
-        if hasattr(self, 'session') and self.session and not self.session.closed:
-            asyncio.create_task(self.session.close())
+    # 移除 __aenter__、__aexit__、__del__，不再持有全局 session