Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-17T23:45:38+00:00	DMARC	—	ABSENT	`b7d77c92cfdd…`
2026-08-17T23:45:38+00:00	SPF	—	VALID	`3c81037a9815…`