Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-19T17:32:33+00:00	DMARC	—	ABSENT	`b7d77c92cfdd…`
2026-08-19T17:32:33+00:00	SPF	—	VALID	`4d4815dd4357…`