Playground Drafts

Return full draft subject+body for every lead in the batch.

Tenant-scope enforced via service.get_batch_drafts which calls _load_campaign_owned(campaign_id, user_id) before any row read. A user who passes another user’s batch_id gets a 404 because the campaign_id is ownership-checked first — the batch filter is only applied WITHIN an authorized campaign scope.

Intended usage from the UI: fetched once when the batch reaches terminal-all (overall pending+running == 0), and on explicit “refresh drafts” actions. NOT called on the 2s poll loop — the status endpoint returns has_draft + subject_preview for that surface.