QA of the #167 follow-up found two defects:
1) renumber() referenced an undefined 'tops' variable in the rAF
re-verification pass, so any wrap toggle that reflowed a partially
filled last visual row left stale (non-idempotent) numbering.
2) rows were derived from per-span heights while the code column also
renders newline text nodes between .codeline blocks, so the gutter
could drift from the code column's real visual rows.
renumber() now measures each .codeline's actual offsetTop and places
every number on the visual row its line starts on (a line wrapping to N
rows gets its number on the first of them), pads filler rows in between,
and self-corrects one frame later if reflow moves any line. Wrap-OFF
path stays unchanged ('1
2
3
4'). Verified in headless Chromium:
gutter/code row alignment exact at 1200px and 640px, toggle cycles
stable, no horizontal scroll, no CSP console errors; go build/test pass.
fen