Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-16T19:38:10+00:00	DMARC	—	VALID	`27a7a44b84c8…`
2026-08-16T19:38:10+00:00	SPF	—	VALID	`16d42a5999af…`