Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-20T20:42:22+00:00	DMARC	—	VALID	`41728f6d14bd…`
2026-08-20T20:42:22+00:00	SPF	—	VALID	`bf0fb21f15be…`