Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-18T08:29:51+00:00	DMARC	—	VALID	`a7d57b5b220c…`
2026-08-18T08:29:51+00:00	SPF	—	VALID	`c7902f5da209…`