Record a suppressed care nudge instead of dropping it silently (#370)

Dropping a sev1-2 care nudge while you're away is right and still happens.
But it was a bare `continue`: no row, no log, so "she dropped it", "the gate
suppressed it" and "the rule never fired" all looked identical afterwards.

Adds a 'dropped' delivery status (migration #12 widens the CHECK constraint;
sqlite can't do that in place, so the table is rebuilt) and records the drop
as one delivery_attempts row plus a log line.

No nudges row for a drop: that table feeds the ignored_rate signal, and a
nudge nobody could see must not count as ignored.

TestVoiceNoSessionFallthroughLeavesOutboxTrail expected exactly one row for
sev1-2 when voice had no session. It now expects the voice failure plus the
drop, which is the point of the change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CGeSZxh1DCtRxmFVSYVGvJ

internal/delivery/routing_table_test.go

@@ -208,10 +208,9 @@ func TestAwayChannelsGetMinimalBody(t *testing.T) {
 // TestCareAwayDropIsRecorded — DESIGN.md's drop is a decision ("a missed water
 // nudge is noise, a missed backup failure isn't"), so it should be visible
 // rather than vanish. Today drop is a bare `continue`: no nudge row, no outbox
-// attempt, no log — nothing an operator can see afterwards.
+// attempt, no log — nothing an operator can see afterwards. now it leaves a
+// 'dropped' outbox row.
 func TestCareAwayDropIsRecorded(t *testing.T) {
-	t.Skip("not implemented: dispatcher.go:149-151 skips a Drop channel with no record; there is no 'dropped' outcome in store/delivery.go:16-21")
-
 	ob := &fakeOutbox{}
 	d := NewDispatcher(Config{Voice: &fakeSink{}, Nudges: &fakeNudgeRecorder{}, Outbox: ob})