Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-17T14:20:43+00:00	DMARC	—	VALID	`f112a7d5f44b…`
2026-08-17T14:20:43+00:00	SPF	—	VALID	`876c427fe12b…`