Also lands the Q111 landed-count addendum left uncommitted at 7c36185 (its
2-line append and its index render were still in the worktree).
Repair: 960469d. Pre-fix cell + 11 ms scheduler gap -> rc 1, dt 0.03897-0.03912
(the observed 0.03909 at 7c36185 minus its 10.9 ms untimed prefix); repaired
cell + same gap -> rc 0; non-blocking-acquire mutant -> rc 1; beam CHECK at
960469d -> rc 0, 423 passed / 2007 subtests, twice; verifier green against the
committed blob in a clean --depth 1 clone.
Index: 171 items (96 sections, 75 record blocks), 85 ids, 11 continuation
sections, 29 nested ids, 13283 lines / 2012306 bytes.