fix(alarms): keep a ringing card out of the swipe, and Undo off the ViewModel scope

A ringing alarm's card no longer swipes or offers Delete: it leads to
the ring screen, and a swipe must not get round the dismiss challenge.
A drag cancelled before release (a ring screen opening on top) never
deletes. Undo restores on the application scope, since a claimed Undo
has no second chance. Closing a cycle and deleting share one teardown.

docs/ARCHITECTURE.md

@@ -1718,7 +1718,9 @@ be a lie; the user who wants that has the enable switch.
 An alarm is deleted by swiping its card towards the end edge, by the card's
 **Delete** custom accessibility action (the same verb for TalkBack and switch
 access, where there is no swipe), or from the editor's top bar. None of them
-asks first. Each is followed by a snackbar on the list ("07:00 alarm deleted",
+asks first. A *ringing* card offers neither the swipe nor the action: it leads
+to the ring screen, and a swipe must not become a way round its dismiss
+challenge. Each is followed by a snackbar on the list ("07:00 alarm deleted",
 **Undo**), as in Google Clock. v1 asked before instead, on the argument that a
 mistaken delete is found at 07:00 rather than now. But a dialog catches no more
 than the snackbar does: both only catch the slip noticed in the moment, and a