feat(route): add mqlaunch thin entrypoint

[MCamner]

Why

Phase 5 of the local-first routing roadmap requires a lossless operator entrypoint without moving routing policy into shell.

What Changed

• add mqlaunch route as a direct delegate to mq-agent route
• preserve every argument and backend exit codes 0, 1, 2, and 127
• register the command under the mq-agent owner and regenerate help
• document the boundary and add an active behavior smoke test

Verification

The targeted smoke test proves arguments with spaces and shell metacharacters remain unchanged, and that delegate exit codes are preserved.