Read External Source Scaffold release-candidate preview metadata

Owner/admin metadata for the External Source Scaffold release-candidate preview route. Returns accepted input shapes, supported workstreams, release evidence requirements, and a forced-false production release/smoke/write authority boundary. It performs no DB writes, PR creation or merge, owner release approval recording, implementation execution, production release, production smoke execution, docs/public discovery mutation, route mutation, Seller OS mutation, trust/ranking mutation, x402/wallet/settlement mutation, provider dispatch, browser automation, memory write/promotion, live finance action, or private Full ECF exposure.