Conflict Detector
Policy SPI: classifies the ConflictType between an incoming proposition and an existing one it appears to contradict.
This separates detecting that two propositions clash (done elsewhere by the reviser) from classifying the clash — is it a genuine contradiction, a revision, or the world simply progressing? Consumers may supply their own implementation; DICE ships a conservative default (AlwaysContradictionDetector) and a temporal one (TemporalConflictDetector).