- apply_delta: DELTA replay arm — fold pre-delta state via back_off,
overlay the field, remove-then-recreate so indexes stay correct
- apply_record/replay loop: dispatch DELTA to apply_delta, drop its
payload back to the log same as INSERT/UPDATE
- stage_flattened_row: compaction's delta-chain path — fold + re-encode
as one fresh INSERT instead of copying the chain
- wo_wal_compact: peek the row's current record kind, flatten deltas,
keep the byte-for-byte copy for chains already at length zero
- test_wal: three new tests — chain-of-three replay incl. secondary
index, compaction flattens to chain length zero (asserts the record
is a full row, not a delta), and the commit-before-repoint crash
window replays the update without ever re-pointing the map
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 7e4ae70d7beb2a2e396a002184bc06f41253decb)