Fourth round of review fixes for the silence-after setting.
onAutoSilence no longer re-arms a ring it measures as inside the window.
After a clock moved back, that check could push the backstop out again
and stretch the ring well past its window. Every writer of the window and
every clock change already re-arms the backstop under the engine lock, so
a backstop that fires has had its window, and it closes the ring as in v1.
A one-shot alarm the resolver switches off as missed also clears a
pending skip flag, as the resolver's other one-shot disable does.
SNOOZE_GRACE is its own ten-minute constant again, not tied to the
setting's default.
Refs #17
makiolaj
0b7af0d57b