Read External Source Scaffold release-execution-evidence preview metadata

Owner/admin metadata for the External Source Scaffold release-execution-evidence preview route. Returns accepted input shapes, supported workstreams, accepted manual release results, release execution evidence requirements, and a forced-false evidence-recording/execution/release/smoke/write authority boundary. It performs no DB writes, evidence recording by helper, release execution start, release decision execution, release executor dispatch, PR merge, owner release approval by helper, 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.