paste-lines.js joined .codeline spans with '\n' text nodes that pre-wrap
renders as extra line boxes, and renumber() counted per-line span heights
(rounding) instead of real geometry, so gutter numbers drifted off their
line starts on wrapped lines. Fix: join spans with '' (blocks need no
newline text), and build one .gutline per visual row measured from the
code body's real height, placing each number at the visual row whose top
matches its .codeline's measured top. Wrap OFF path unchanged. Mobile
font-size rule added so gutter row pitch matches code rows at 375x812.
- splitLines(): join .codeline blocks with "" not "\n" — newline text
nodes under pre-wrap rendered an extra line box per logical line, so
every gutter number drifted one row per line
- renumber(): geometry-driven placement — one gutline per visual row of
the code body, each number assigned to the row matching its line's
measured offsetTop; verified second pass re-runs if a partially-filled
last wrapped row reflows after the gutter rebuild
- app.css: mobile media query gives .code .gutter the same 13px font as
.code so gutter rows and code rows share one line box at 375px
Verified in local build with headless chromium (long unbroken token on
line 5, wrap ON): all numbers align with line starts, no misalignment,
no horizontal scroll at 1400x900 and 375x812.