Codr v2.30.2

• A second codr serve on the same data directory now fails at start with a clear message instead of replacing the
  live hook socket. Before, the running server kept listening on a socket that no longer had a name, and every push
  that carried commits was rejected with "hook failed".
• serve closes the hook socket when it stops on a later start-up error, so it no longer leaves a dead socket file.
• /healthz dials the hook socket: a dead hook path answers 503 with "ok":false,"hooks":"down"; a live one adds
  "hooks":"ok". codr doctor also dials the socket instead of only checking that the file exists.
• A failed hook call prints its cause on a second line, and the server logs requests it cannot decode.