No 'already running' guard existed — a relaunch (array stop/start that
doesn't kill the old node process) would exec straight into node, hit
EADDRINUSE on the port, and exit 1 within ~1s. array_started.sh correctly
reported that as a failure, even though the prior listener instance was
still healthy and serving webhooks the whole time. Confirmed live: the
node process from 2026-06-23 (PID 25977) is still running today, and the
2026-07-03 array start logged this exact false failure.
Added acquire_lock "continuous" before the exec — an existing, documented
common.sh mode (skip gracefully if a healthy instance is running) that
wasn't actually used anywhere in the codebase yet.