Round 2 mutation-checked round 1's own fix and found the one line it left
uncovered: every table row was an integer, so `Math.floor(sec)` in the new
seconds tier could be deleted or swapped for round/ceil with the suite still
green — exactly the "later cleanup removes it as redundant" failure the fix's
comment claims to prevent. Two fractional rows kill all three mutants.
peter
3cfdb36f06