- wo_row_borrow's keys arm folded at hget()'s DURABLE offset even
when an earlier update in the same drain had only a PENDING
re-point
- idx_remove_row then hashed the pre-first-update value, found no
matching bucket entry (already moved by the earlier update), and
idx_add_row added a second one — N same-drain updates leaked N-1
entries, unbounded, nothing reclaims them but a restart
- now prefers wo_wal_repoint_offset1() over the durable offset, same
as back_off already does, closing it for every borrow
- new test: 5 updates to one row in one drain, assert exactly one
index entry — fails (5) before the fix, passes (1) after
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit d4b12d1908e574419c7af2411e52d02623f7e5b7)