Stable, server-controlled authenticated principal identity. Never a credential.
Stable digest of the seller identity and endpoint. Never a credential.
OptionalexpiresSDK-normalized RFC 3339 seller hold expiry, when the proposal supplied one.
Optionalcanonical
Serializable, immutable evidence retained from one established seller proposal. This deliberately excludes raw seller responses, credentials, coordinator owners, timers, listeners, and live mutable references.