gatelineAPI reference
SUPERSEDE_EXIT_CODE: 75

Exit code gateline up (and gateline-orchestrator watch) use once they have drained and stopped in response to a confirmed supersede, so a supervisor restarts them on fresh code. 75 is EX_TEMPFAIL from <sysexits.h> — "temporary failure, please retry" — chosen because it plays well with launchd's KeepAlive and systemd's RestartForceExitStatus=75.