An alert that resolved while its firing notification was still in the
grouping window or waiting in the persistent queue (alert delay pushes
activation close to resolution; quiet-hours replay defers delivery)
produced a recovery-only notification: CancelAlert dropped the queued
firing, but LastNotified had been set optimistically at dispatch, so
the resolved-notification gate believed the firing had been sent.
CancelAlert now reports whether it cancelled a firing notification that
had not been delivered (grouping window entries and pending queue rows;
mid-send rows are excluded because their delivery may still complete),
and handleAlertResolved suppresses the recovery in that case. This also
covers the quiet-hours replay bypass: a recovery only follows a deferred
firing if the replay was actually delivered.
Addresses #1553
rcourtman