Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-17T18:00:23+00:00	DMARC	—	VALID	`36464d2c3bed…`
2026-08-17T18:00:23+00:00	SPF	—	VALID	`3ffac9225bb3…`