Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@app.js`:
- Around line 291-293: Axis label elements appended by renderAxes()
(text.axis-label) are not removed on rerender, causing duplicates; update the
cleanup in renderChart() to also remove those labels by extending the selector
used on g (the one currently targeting "g.axis-y, g.axis-x, .milestone-marker,
path.layer, .scrubber-line, rect[fill='transparent']") to include
"text.axis-label" so renderAxes() can safely re-append "Time" and "Lines of
Code" without stacking; ensure the change targets the same g.selectAll(...) call
that precedes svg.select("defs").selectAll("linearGradient").remove() so both
gradients and axis labels are cleaned up.
- Around line 909-932: renderFossils() currently re-attaches click/keydown
handlers to the persistent elements 'fossil-genesis' and 'fossil-survivor' on
every render causing duplicate opens; modify the code that binds openLink, the
click listener and the keydown listener so it only binds once (e.g., check/set a
flag like card.dataset.listenersBound and skip adding listeners if present, or
use addEventListener with a bound named function and remove existing listeners
first), and apply the same single-bind pattern to the renderLegend() binding for
'`#chart-legend`' to prevent listener accumulation.

In `@DESIGN.md`:
- Line 13: The DESIGN.md `frost` token is documented but not implemented in the
CSS; add a CSS variable and use it. Define --frost: oklch(45% 0.015 255) in the
:root selector of style.css and replace or add any relevant color usages (e.g.,
components that should use frost) to reference var(--frost); ensure the token
name matches `frost` from DESIGN.md so the documented value is actually applied.

In `@index.html`:
- Around line 262-264: Remove the development live-reload snippet that injects
an external HTTP script: delete the HTML block between the <!--
impeccable-live-start --> and <!-- impeccable-live-end --> markers (the <script
src="http://localhost:8401/live.js"></script> line) so it does not ship on main;
alternatively gate inclusion behind a dev-only build flag or environment check,
but do not leave the unconditional script tag or markers in the production HTML.
- Line 105: The SVG with id "main-chart" uses role="img" which blocks
interactive/focusable descendants from being exposed to assistive tech; remove
role="img" (or replace it with a more appropriate interactive role such as
role="group" or role="application") and ensure the element still has an
accessible name via aria-label or aria-labelledby (keep aria-label="Lines of
code over time, stacked area chart showing code composition by year of origin"
or switch to aria-labelledby pointing to a visible heading) so the chart remains
accessible and interactive elements inside are announced correctly.

---

Nitpick comments:
In `@index.html`:
- Around line 115-116: The help-icon spans use data-tooltip for visible text but
are not exposed to AT; update each <span class="help-icon" tabindex="0"
data-tooltip="...">?</span> (all occurrences of class "help-icon") to also
include an aria-label attribute set to the same string as data-tooltip so screen
readers receive the tooltip content (i.e., copy the data-tooltip value into
aria-label for the spans at the five locations).