Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-19T18:34:55+00:00	DMARC	—	VALID	`d1c5d6c1df9b…`
2026-08-19T18:34:55+00:00	SPF	—	VALID	`48fb8e9fb49c…`