fix(alarms): name a pause's last day, and switch on an alarm given a date

"Paused, back on" named the day after the pause, which for a weekday
alarm can be a Saturday it never rings on. A pause under way now reads
"Paused through Wed, Oct 28".

Picking a date on a switched-off alarm switches it on, the pause picker
cannot confirm a range that is already over, a spent pause stored with
its ends reversed is cleared too, and the widget formats its date in the
app's own locale.

docs/ARCHITECTURE.md

@@ -1341,7 +1341,8 @@ date only while its occurrence is still ahead and a pause only while its last
 day has not passed. The editor's date picker starts at `AlarmSchedule.earliestDate`,
 the date of the alarm's next plain occurrence, so neither a past day nor
 today-after-the-time-has-gone can be picked; moving the time earlier than now
-on a date set for today drops the date. Picking a repeat day clears the date
+on a date set for today drops the date. Picking a date switches the alarm on, since
+a switched-off alarm would read "Scheduled for" and stay silent. Picking a repeat day clears the date
 and clearing the last one clears the pause, as in Google Clock. The
 `AlarmClock` contract cannot express either field, so `SET_ALARM` never
 re-uses an alarm that carries one (§17).