Delete Custom Skill

Delete a skill: drop its attachments, its row, and its bundle.

The row is soft-deleted to keep an audit trail, but the bundle objects are removed — there is no undelete, so retaining them would grow storage for a recovery path that does not exist. The row is marked first so the user's delete is durable; a failed object delete is logged rather than raised, since the skill is already gone from their view.

The row is read under FOR UPDATE because bundle_token and files are read here and then used to delete objects. Without the lock a concurrent bundle write can land its compare-and-swap between the two, and this request deletes the prefix that write just retired while the row now names one whose objects nothing will ever remove.