Register the weekly suggestions schedule (Feature 20)

suggest.Service.WeeklySchedule fires at the household suggestions_dow and
suggestions_time (default Sunday 08:00) with period key
suggestions_weekly:YYYY-Www and starts a scheduled batch through the same
service and job as the API, via the new StartScheduledBatch(week).
StartBatch now refuses the scheduled trigger.

new_suggestions is still emitted only where Feature 19 put it, in the
transaction that stores a batch's Side quests. A scheduled batch is now
keyed new_suggestions:YYYY-Www by the week carried in its job, so a
batch caught up late keeps its own week's key; a manual batch stays keyed
by its id. The title counts the new Side quests. A batch whose AI call
fails stores nothing and sends nothing; the failure is in ai_runs.

Fake-clock tests in internal/scheduler cover one batch and one
notification per week, settings-driven fire time, AI failure, restart,
late catch-up and a batch already under way.

Maestro task 459aab71-5c3d-4853-9855-236a3602b1e0

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/chat/messages.go

@@ -77,13 +77,15 @@ func DayOfReminder(date store.LocalDate, dinnerID, name string) notify.Event {
 	}
 }
 
-// NewSuggestions is the new_suggestions event of suggestion batch batchID,
-// made in the week starting on week, naming its Side quests.
-func NewSuggestions(batchID string, week store.LocalDate, names []string) notify.Event {
+// NewSuggestions is the new_suggestions event keyed by id, the ISO week
+// ("2026-W41") of a scheduled suggestion batch or the batch id of a manual
+// one, of the week starting on week: how many new Side quests there are,
+// and their names.
+func NewSuggestions(id string, week store.LocalDate, names []string) notify.Event {
 	return notify.Event{
 		Type:  notify.NewSuggestions,
-		Key:   string(notify.NewSuggestions) + ":" + batchID,
-		Title: "New Side quests are in",
+		Key:   string(notify.NewSuggestions) + ":" + id,
+		Title: count(len(names), "new Side quest is in", "new Side quests are in"),
 		Body:  nameList(names),
 		URL:   "/discover",
 		Week:  week,