fixes MCP servers never coming up on windows

This fixes https://github.com/sigoden/llm-functions/issues/185 MCP server cannot start on Windows ``` PS D:\projects\scratch\llm-functions> argc mcp start On Windows... Start MCP Bridge server... Install node dependencies... npm_package_dir: D:\projects\scratch\llm-functions\mcp\bridge npm error code ENOENT npm error syscall open npm error path D:\projects\scratch\llm-functions\package.json npm error errno -4058 npm error enoent Could not read package.json: Error: ENOENT: no such file or directory, open 'D:\projects\scratch\llm-functions\package.json' npm error enoent This is related to npm not being able to find a file. npm error enoent npm error A complete log of this run can be found in: C:\Users\Sid31\AppData\Local\npm-cache\_logs\2025-05-08T01_23_52_939Z-debug-0.log ```