Function classify_receipt 

pub fn classify_receipt(
    receipt: &PublishReceipt,
    observed: Option<&RemoteObservation>,
) -> VerifyOutcome

Classify a PublishReceipt against an optional remote observation — the pure core of every adapter’s verify (ADR-0002 §1, ADR-0003 state table).

• observed == None (the lookup could not be performed) ⇒ VerifyOutcome::Unknown — an outage is never read as Missing.
• version absent from the remote set ⇒ VerifyOutcome::Missing.
• version present, both digests known and unequal ⇒ VerifyOutcome::Conflicts.
• version present, digests equal or a digest is unobservable ⇒ VerifyOutcome::Matches.