Restore an earlier version of a skill

SPENDS NOTHING. Publishes the old snapshot as a NEW version, live for the next run - agents and workflows using the skill pick it up. Append-only, so the restore can itself be rolled back. Routine-managed skills refuse (403). A restored graph with record steps or a record trigger needs the same object scopes as a create or an update (403 missing_scopes), a restored graph whose snake_case and camelCase node keys disagree is refused (422 conflicting_node_keys), and a restore that changes such a workflow's graph is refused (403 owner_or_admin_required) unless the key's member owns the workflow or administers the org. The version's graph is read first to run those checks: 404 when it cannot be found (unknown skill or version).