1. Add a local (stdio) server

A host reads an `mcpServers` object (e.g. in claude_desktop_config.json or a project `.mcp.json`). Each KEY is a server name; each VALUE describes how to start it. A LOCAL server uses the stdio transport, so you give the `command` to run plus its `args` — the host launches that subprocess and speaks JSON-RPC over its stdin/stdout. Here `npx` runs the published filesystem server, scoped to /tmp.