PropositionStoreDriftSweep

Where candidates are read from and quarantined copies are saved back to. The base persistence port: a sweep reads by context and saves, so requiring vector search, graph traversal and temporal query alongside would shut a plain store-and-retrieve backend out of drift work over capabilities it never uses.

Told about each real status transition as a PropositionStatusChanged, so a consumer like ProjectionLineageStaleCascade hears about a quarantine, and about a release, without depending on whichever concrete propositions store happens to be wired in. Defaults to a no-op: everything else here holds with nobody listening.