fix: preserve PATHEXT for stdio mcp servers on windows (#5822)

* fix: preserve PATHEXT for stdio mcp servers on windows

* chore: delete test_mcp_client.py

---------

Co-authored-by: Soulter <905617992@qq.com>

astrbot/core/agent/mcp_client.py

@@ -1,5 +1,7 @@
 import asyncio
 import logging
+import os
+import sys
 from contextlib import AsyncExitStack
 from datetime import timedelta
 from typing import Generic
@@ -45,6 +47,22 @@ def _prepare_config(config: dict) -> dict:
     return config
 
 
+def _prepare_stdio_env(config: dict) -> dict:
+    """Preserve Windows executable resolution for stdio subprocesses."""
+    if sys.platform != "win32":
+        return config
+
+    pathext = os.environ.get("PATHEXT")
+    if not pathext:
+        return config
+
+    prepared = config.copy()
+    env = dict(prepared.get("env") or {})
+    env.setdefault("PATHEXT", pathext)
+    prepared["env"] = env
+    return prepared
+
+
 async def _quick_test_mcp_connection(config: dict) -> tuple[bool, str]:
     """Quick test MCP server connectivity"""
     import aiohttp
@@ -214,6 +232,7 @@ class MCPClient:
                 )
 
         else:
+            cfg = _prepare_stdio_env(cfg)
             server_params = mcp.StdioServerParameters(
                 **cfg,
             )