Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-17T18:32:06+00:00	DMARC	—	VALID	`07f35493f360…`
2026-08-17T18:32:06+00:00	SPF	—	VALID	`b8212d2f2f08…`