Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-19T18:34:52+00:00	DMARC	—	VALID	`c99444c5192b…`
2026-08-19T18:34:52+00:00	SPF	—	VALID	`924db2d1bd23…`