POST /pairing/unpair

Revokes the local member record for the given peer. Success is signalled by 204 No Content with no body (ADR-008 §B Rule 3 — 204 endpoints are NOT enveloped). Errors flow through the shared ApiError carrier and therefore serialize to ApiErrorResponse { code, message, details? } on the wire — the dedicated PairingApiErrorResponse contract only covers the retired libp2p pairing routes, not this revoke path.