Not named isExpired: the deprecated isExpired also returns true for a swept VTXO, and
two same-named predicates with different truth conditions is how a call site gets silently
rewired.
Height-based expiry is only evaluated when now.height is supplied.
Whether a virtual output's batch expiry has passed. Pure expiry — swept is a separate fact, ORed in explicitly by canSpendOffchain / canRecoverOnchain.