Delete Template

Delete a template owned by the caller's workspace. The delete is a soft delete — the record is hidden from the gallery and all visibility checks immediately, but is not physically removed. Any workflows previously cloned from this template are unaffected; clone creates an independent copy of the definition at clone time. Restrictions: - Only the owning workspace may delete its templates (403 otherwise). - Platform starter templates (`is_starter=true`) cannot be deleted (403). Requires workspace `editor` role or higher.