- Force-exit timer now distinguishes serverClosed from managersStopped.
Was: if (closed) return → suppressed timer when manager hung after
server.close fired (the original bug).
Now: if (managersStopped) return → timer fires only when full drain
(HTTP close + all managers stopped) completes before the deadline.
- Added _safeEmit() helper that wraps this.emit() so a buggy listener
throwing during 'shutdown' or 'closed' doesn't abort the shutdown
sequence. Each failed listener is logged via the structured logger.
- Added 4 new tests covering: hung manager after HTTP close,
throwing shutdown listener, throwing closed listener, and the
fast-drain happy path that clears the timer cleanly.