grex-mcp — MCP-native server for grex (M7).

Stage 5 wires the [rmcp] framework: the server speaks the MCP 2025-06-18 wire protocol over any [rmcp::transport] (stdio in production, [tokio::io::duplex] in tests). The handshake + tools/list (returning empty) + transport-close shutdown are live; the 11 tool handlers land in Stage 6, and cancellation in Stage 7.

Stdout discipline

The MCP stdio transport multiplexes only JSON-RPC bytes on stdout. All diagnostics MUST go to stderr. [GrexMcpServer::run] installs a tracing_subscriber::fmt writer pinned to stderr — idempotently, so test reuse and serve-from-CLI both work. The no_println_lint.rs integration test enforces zero println! / print! macros under src/ to prevent regressions.