Turn the tool into an MCP server

The parser and pack loader from the previous exercise are reused unchanged, with a thin MCP layer on top. This answer uses the current official TypeScript SDK (v2: @modelcontextprotocol/server 2.4.0, implementing the 2026-07-28 spec). In it, a server is a factory function that creates an McpServer and calls registerTool with a Zod input schema, and serveStdio(factory) serves it. The decision that matters most is which checks go where: the schema checks the shape of a call (the model sees section as an enum), and the handler checks its meaning (is this title in the pack?).