approximately v2.22.0

• the stdio flush: the MCP server answers over real pipes. a subprocess smoke of the flagship entry point found the biggest bug of the night — the serve loop wrote each response with stdout.write and never flushed, and piped stdout block-buffers, so approximately mcp hung against every real client (Claude Desktop, Zed, anything that pipes). Every prior test drove handle_request in-process; the transport was never exercised. cmd_mcp now flushes per response, and a real-pipe subprocess smoke (tools/list, doctor, initialize) pins the transport forever. 1 test that could only exist as a subprocess.

Full Changelog: v2.21.4...v2.22.0