Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-18T15:07:36+00:00	DMARC	—	VALID	`923b30fcb4b8…`
2026-08-18T15:07:36+00:00	SPF	—	VALID	`876c427fe12b…`