docs: redesign the results UI

[colinhacks]

A visual refresh of the results site. docs/ only — no data or benchmark changes, and all existing functionality (benchmark/runtime filters, sort, light + dark via the OS preference) works as before.

Before:

After:

What changed:

• Replaces water.css and the inline styles with a small stylesheet: filters in a sticky sidebar, the chart on a card, the benchmark descriptions in a grid of cards. Single-column below 900px.
• New chart palette with one stable color per benchmark. The four colors pass colorblind-separation (CVD) checks against both surfaces; the old Set3 pastels also colored the value labels, which made them hard to read in light mode.
• Every row gets a full-width track, and a benchmark a library doesn't implement reads as n/a on an empty track. Previously those rows printed 0 against an axis where zero is indistinguishable from a missing bar.
• The plot is sized from its container rather than a fixed 600px, so value labels and the last axis tick no longer get clipped between roughly 1000 and 1300px wide. Long library names truncate on narrow screens instead of squeezing the bars out of view.
• Selecting more than one runtime version now labels each bar with its version. Previously the repeated bars were the same color with nothing to tell them apart.
• Compact SI axis ticks (20M) and monospaced value labels.
• The chart SVG re-renders on an OS color-scheme change; previously it kept the old label colors until reload.
• The Star/Fork buttons have rendered as bare text links since the Vite migration dropped the github-buttons script; they're now styled links with inline octicons, no external script.
• Fonts: Inter and JetBrains Mono from Google Fonts.

npm run lint and npm run build pass in docs/.

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