Read External Source Scaffold release-decision preview metadata

Owner/admin metadata for the External Source Scaffold release-decision preview route. Returns accepted input shapes, supported workstreams, accepted owner release decisions, release decision requirements, and a forced-false decision/release/smoke/write authority boundary. It performs no DB writes, 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.