fix(mcp): add 30s timeout to MCP tool calls to prevent agent hangs

nanobot/agent/tools/mcp.py

@@ -1,11 +1,15 @@
 """MCP client: connects to MCP servers and wraps their tools as native nanobot tools."""
 
+import asyncio
 from contextlib import AsyncExitStack
 from typing import Any
 
 import httpx
 from loguru import logger
 
+# Timeout for individual MCP tool calls (seconds).
+MCP_TOOL_TIMEOUT = 30
+
 from nanobot.agent.tools.base import Tool
 from nanobot.agent.tools.registry import ToolRegistry
 
@@ -34,7 +38,14 @@ class MCPToolWrapper(Tool):
 
     async def execute(self, **kwargs: Any) -> str:
         from mcp import types
-        result = await self._session.call_tool(self._original_name, arguments=kwargs)
+        try:
+            result = await asyncio.wait_for(
+                self._session.call_tool(self._original_name, arguments=kwargs),
+                timeout=MCP_TOOL_TIMEOUT,
+            )
+        except asyncio.TimeoutError:
+            logger.warning("MCP tool '{}' timed out after {}s", self._name, MCP_TOOL_TIMEOUT)
+            return f"(MCP tool call timed out after {MCP_TOOL_TIMEOUT}s)"
         parts = []
         for block in result.content:
             if isinstance(block, types.TextContent):