A `#commit` frame's `blocks` held only the CIDs the commit's own history diff marked as created, which is what a consumer holding the previous state needs but not what a relay holding none of it can invert: a split or merge pulls in a Merkle search tree node neither side's own key touched, and a real `indigo` `cmd/relay` run against two live instances failed exactly there — "reading MST from CAR file: ipld: could not find <cid>" on every non-first commit. `Committed::blocks` now unions every touched key's covering proof — `Repository::covering_proof`, new here and built on the tree's own `covering_proof` — with the blocks the commit created, so a frame carries what `com.atproto.sync.subscribeRepos`'s inductive verification needs to reconstruct `prevData` from nothing. Change-Id: I029c2200c519b645e4c206d8051ac8a42d949425