feat(11-02): add schedule:run as a scheduler process and a cron --once mode

- schedule:run runs a worker on the scheduled queue with every plugin's periodic jobs
- schedule:run --once runs entries due in the current app.timezone minute without River,
  warns and skips unregistered commands, and returns the first command error
- summer schedule:run delegate forwards --once
- tests for --once minute matching, forged-entry skipping (T-11-09) and ByPeriod dedupe

modules/conga/scheduler.go

@@ -145,16 +145,8 @@ func (m *Manager) runScheduled(ctx context.Context, a ScheduledCommandArgs) erro
 // at Warn and skipped (skipped true, nil error); a command error is logged
 // with the duration and returned.
 func callScheduled(ctx context.Context, app *backpack.App, log *slog.Logger, command string, args []string, out io.Writer) (bool, error) {
-	var cat *bonfire.Catalog
-	if app != nil {
-		cat, _ = app.Lookup[*bonfire.Catalog]()
-	}
-	if cat == nil {
-		log.Warn("schedule: no command catalog published; skipping", "command", command)
-		return true, nil
-	}
-	if !cat.Has(command) {
-		log.Warn("schedule: command not registered; skipping", "command", command)
+	cat, ok := scheduledCatalog(app, log, command)
+	if !ok {
 		return true, nil
 	}
 	start := time.Now()
@@ -168,6 +160,24 @@ func callScheduled(ctx context.Context, app *backpack.App, log *slog.Logger, com
 	return false, nil
 }
 
+// scheduledCatalog returns the app's catalog when it holds command. A missing
+// catalog or command is logged at Warn and reported as false.
+func scheduledCatalog(app *backpack.App, log *slog.Logger, command string) (*bonfire.Catalog, bool) {
+	var cat *bonfire.Catalog
+	if app != nil {
+		cat, _ = app.Lookup[*bonfire.Catalog]()
+	}
+	if cat == nil {
+		log.Warn("schedule: no command catalog published; skipping", "command", command)
+		return nil, false
+	}
+	if !cat.Has(command) {
+		log.Warn("schedule: command not registered; skipping", "command", command)
+		return nil, false
+	}
+	return cat, true
+}
+
 // logWriter logs each output line of a scheduled command at Info.
 type logWriter struct {
 	log     *slog.Logger
@@ -214,3 +224,6 @@ func (w *logWriter) emit(line string) {
 	}
 	w.log.Info(line, "command", w.command)
 }
+
+// scheduleNow is the clock of schedule:run --once (tests replace it).
+var scheduleNow = time.Now