Watch flushed the alert queue in the scan goroutine. With a hung ntfy
(accepts, never answers until the 10 s timeout) and a full queue, one
flush took ~6 notify timeouts, so a planted symlink stayed readable for
several intervals instead of at most one.
Delivery now runs in its own goroutine that owns the queue. The scan
hands alerts over on a bounded channel without blocking; an alert that
does not fit is counted in the never-dropped summary, so the
"delivered or counted" property holds.
Repro test (interval 50 ms, notifier latency 40 ms, full queue): worst
link lifetime 243 ms before, under 2 intervals after.
Closes#164
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>