* feat(tiering): model provider version capabilities * feat(tiering): persist opaque remote versions * fix(tiering): gate remote version state safely * fix(tiering): preserve remote version state on delete * fix(tiering): accept unversioned transition responses * fix(tiering): replay exact cleanup journals * test(tiering): pin empty exact cleanup guard * test(tiering): accept strict missing journal errors * test(tiering): exercise free-version identity guard * test(tiering): reach destination identity guard * test(tiering): persist version identity drift * test(tiering): bind version drift fixture --------- Co-authored-by: houseme <[email protected]>