A kind can now be made service-only: Runner.Enqueue, and so
POST /api/v1/jobs, refuses it with 400 service_only_kind, and only its
typed Kind enqueues it. draft_week is service-only, so StartDraft and
its one-draft-in-flight-per-week rule is the only way to start a draft;
a confirmed draft_week posted to /api/v1/jobs can no longer run beside
the week's unconfirmed draft.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>