Phase 6 follow-up: today-and-future events, one write per school-wide event

Two corrections found while preparing the first live run:

- A scan that runs late in the day still records today's school events; the
  candidate window now starts at the local start of day instead of "now".
- The Compass week calendar is school-wide, so one event is stored against each
  child. Write it once, with no child prefix in the title, and record the same
  Home Assistant event id on every child's item. A per-child event still keeps
  the child's name.

Also report pending events as events, not rows, in `school calendar status`.
Tests cover the window and the de-duplication.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

cmd/school/calendar.go

@@ -125,11 +125,14 @@ func calendarStatus(args []string) {
 		os.Exit(1)
 	}
 	now := time.Now().In(cfg.Location)
-	candidates, err := st.CalendarCandidates(ctx, nil, nil, now, 0)
+	candidates, err := st.CalendarCandidates(ctx, nil, nil, calendar.StartOfDay(now), 0)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "school calendar:", err)
 		os.Exit(1)
 	}
+	// Count events, not rows: a school-wide event is stored against each
+	// child but written once.
+	pendingEvents := len(calendar.GroupDuplicates(candidates))
 
 	if asJSON {
 		out := struct {
@@ -145,7 +148,7 @@ func calendarStatus(args []string) {
 			BaseURL:     haHost(cfg.Calendar.BaseURL),
 			Entity:      cfg.Calendar.EntityID,
 			TokenSet:    cfg.Calendar.Token != "",
-			Pending:     len(candidates),
+			Pending:     pendingEvents,
 			ReloadedAt:  now.Format(time.RFC3339),
 			PushSummary: summary,
 		}
@@ -171,7 +174,7 @@ func calendarStatus(args []string) {
 	} else {
 		fmt.Printf("reachable       yes\n")
 	}
-	fmt.Printf("pending events  %d (important, not in the calendar yet)\n", len(candidates))
+	fmt.Printf("pending events  %d (important, not in the calendar yet)\n", pendingEvents)
 	fmt.Printf("pushes          %d (%d failed)\n", summary.Total, summary.Failed)
 	if summary.Last != nil {
 		state := "ok"