The stats collector (~2s) and mouse-mode sync (5s) ran execSync (pgrep/ps/
list-panes, 5s timeout each) per session on the server's single thread,
blocking the event loop. With several sessions or a momentarily slow tmux this
froze port 3000 for seconds-to-tens-of-seconds while the process stayed alive
and other ports were unaffected — self-healing, so it never restarted and the
60s loopback healthcheck missed it. Convert these hot-path calls to execAsync.
Also add an always-on event-loop lag monitor (utils/event-loop-monitor.ts) that
logs stalls >=1s to the web log, so this otherwise-invisible class of incident
leaves a quantified, timestamped trace.
Co-authored-by: Teigen <teigen@TeigendeMac-mini.local>
