Authentication history

Immutable persisted observations.

Observed	Signal	Selector	Verdict	Fingerprint
2026-08-18T17:12:40+00:00	DMARC	—	VALID	`d6414eb1ea5d…`
2026-08-18T17:12:40+00:00	SPF	—	ABSENT	`b081350f91db…`