CVD-safe default categorical palette

[FarhanAliRaza]

Summary

Replaces the Tableau10 default categorical palette with an eight-slot CVD-safe palette (§20/§36 default theme).

Why: Tableau10's adjacent red/green pair collapsed to ΔE 1.2 under deuteranopia — effectively indistinguishable — and slots 1/5/7/9/10 sat below the chroma floor.

The new palette keeps every step in the OKLCH lightness band shared by light and dark surfaces (L 0.48–0.67) and validates against both reference surfaces (#fcfcfb / #1a1a19):

• worst adjacent-pair CVD ΔE 8.5 (Machado–Oliveira–Fernandes protan/deutan, ≥8 target)
• worst adjacent normal-vision ΔE 19.1 (≥15 floor)
• chroma ≥ 0.10 and ≥3:1 contrast for every slot on both surfaces

The slot order is the safety mechanism — adjacency drives the ΔE gate — so the config comment now warns against re-ordering or extending without re-running the validator.

Also in this PR

• Updated the hardcoded segment colors in the Reflex demo app and the visual-regression chrome shell to the new slots.
• Regenerated examples/reflex/assets/charts/*.html, which also picks up the current embedded render client (colormap stops, colorbar chrome CSS) from recent main commits.

Checks

• pre-commit run --all-files, ruff check, ruff format --check all pass.

[codspeed-hq]

Merging this PR will not alter performance

✅ 94 untouched benchmarks
⏩ 1 skipped benchmark¹

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_{Comparing cvd-safe-default-palette (5701f77) with main (8ace307)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩