Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-18T18:45:53+00:00	DMARC	—	VALID	`3a43455cb6f4…`
2026-08-18T18:45:53+00:00	SPF	—	VALID	`c97087e33545…`