makeupDiff replays post-snapshot changes onto the compacted volume. For a
replayed deletion it appended a tombstone to the new .dat but recorded the
.idx entry with offset 0. When that deletion is the last replayed change the
tombstone lands at the .dat tail, and the post-commit integrity check skips
offset-0 entries, so it sees 32 trailing bytes it can't account for and flips
the volume read-only, reloading it as a SortedFileNeedleMap instead of the
writable map.
Record the tombstone's real .dat offset, matching the normal delete path; the
needle map still treats it as deleted off the negative size, so lookups are
unchanged. Mirror the same fix into the Rust volume server.