Minimal MCP (Model Context Protocol) server over stdio.

Reads line-delimited JSON-RPC 2.0 from stdin and writes responses to stdout. Exposes tools for par-term ACP integrations:

• config_update: writes configuration changes to a file for the main app to pick up
• terminal_screenshot: requests a live terminal screenshot from the app via a file-based IPC handshake (with an optional fallback image path for non-GUI test harnesses)

Module layout

• [jsonrpc] — JSON-RPC 2.0 wire types, response helpers, and stdout framing
• [ipc] — IPC path resolution, atomic writes, and restricted-permission helpers
• [tools] — tool registration, descriptors, and dispatch
• [tools::config_update] — config_update tool handler
• [tools::screenshot] — terminal_screenshot tool handler