feat: add theme builder and contrast tooling to color palette generator

[alexlvrs]

What this does

Updates the Color Palette Generator app (apps/eds-color-palette-generator):

• Theme builder + tooling — adds the theme builder as the main page, plus contrast checker and palette editor routes (a71f92b1).
• Lint fixes — resolves 6 react-hooks ESLint errors + 1 warning that surfaced when the theme-builder code moved to /; behaviour-preserving (00aeec26).
• Restructure — promotes the theme builder to the root route, moves the legacy generator to /old, reorganises components into docs/ old/ shared/ themebuilder/, removes unused contrast helpers, updates e2e specs (f80938bd).

Verified locally: lint 0 errors / 0 warnings, types clean, test:run 126/126, and the app was driven end-to-end (theme builder tabs, contrast table, donut chart, component preview, /example, /palette) with no console or hydration errors.

⚠️ Open questions for the reviewer (need a developer's call)

Two items are intentionally not in this PR — left in the local working tree pending your decision (so they won't show in the diff):

1. pnpm-lock.yaml — the local checkout has a ~500-line lockfile churn (native binary variants) with no package.json change. Looks like an install artifact, not intentional. Recommendation: discard (git checkout pnpm-lock.yaml) unless deliberate.
2. plan/*.prompt.md (fix-lint-failures, restructure-palette-generator) — untracked prompt docs. Commit them as documentation, or leave them out? Your call.

Notes

• Target main. This app is not a release-please-tracked package, so merging won't trigger a version bump.

[alexlvrs]

Poke @eddiman has I wasn't sure about this thingy :)

[pomfrida]

@claude review

[claude]

Claude finished @pomfrida's task in 2m 30s —— View job

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Code Review — Color Palette Generator theme builder

• Read the PR diff and understand the changes
• Review theme builder + contrast tooling
• Review shared utils (color, palette, urlState)
• Check accessibility, correctness, and conventions
• Post review feedback

Reviewed against origin/main. This is an internal app (not a release-tracked package), so the correctness/a11y bar is lower than for the component library — but a few things are worth your attention. Overall the restructure is clean and the anchor-preservation change in color.ts looks sensible.

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🔴 Dependency downgrades in package.json (likely the real cause of the lockfile churn)

apps/eds-color-palette-generator/package.json downgrades a batch of dependencies relative to main and removes one:

Package	main	this PR
next / eslint-config-next / @next/eslint-plugin-next	16.2.9	16.2.4
react / react-dom	^19.2.6	^19.2.4
@types/react	^19.2.15	^19.2.14
lucide-react	^1.21.0	^1.12.0
@playwright/test	^1.61.1	^1.59.1
tailwindcss / @tailwindcss/postcss	^4.3.1	^4.2.4
vite / vite-plugin-dts / vitest	^8.1.0 / ^5.0.3 / ^4.1.9	^8.0.10 / ^4.5.4 / ^4.1.5
tsx	^4.22.4	^4.21.0
@microsoft/api-extractor	present	removed

Your PR description says the lockfile churn has "no package.json change" — but there is a committed package.json change here, and it's a broad downgrade. This looks like the branch was created before main picked up the dependency bumps (e.g. 7b3005e chore(deps): bump the all-dependencies group) and never re-synced. This is almost certainly what's generating the ~500-line lockfile delta, and committing a downgraded package.json without the matching lockfile will break pnpm install --frozen-lockfile in CI.

Recommend restoring these to match main unless the downgrade is deliberate (and if it is, say why in the PR). Fix this →

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🟠 Correctness

urlState.ts — delimiters in names/values aren't escaped. serializePalette joins palettes with ,, anchors with @, and uses : / = as separators, but the palette name is written raw (only deserializePalette calls decodeURIComponent). A palette named Blue, Green or containing :/@ will round-trip incorrectly. encodeURIComponent the name (and anchor value) on serialize to match the decode side. (urlState.ts:31-39)

updateURL debounce timer is never cleared on unmount. The module-level debounceTimer (urlState.ts:128-142) fires 300 ms after the last change with no cleanup in the page.tsx effect, so a trailing replaceState can run after navigation away. Return a cleanup from the effect, or expose a cancel. (page.tsx:61-67)

Index-based React keys with editable/removable rows. PaletteInputPanel maps palettes with key={i} (PaletteInputPanel.tsx:122) while AnchorRow holds per-row local state (localValue, isValid) and the parent tracks expandedIndex by position. Removing/reordering a palette shifts indices, so local input state and the expanded row bind to the wrong palette. Prefer a stable id per palette/anchor. Fix this →

ContrastTable palette buttons keyed by p.name (ContrastTable.tsx:72) — two palettes with the same name collide. Also fine to use a stable id.

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🟡 Accessibility

• Icon-only buttons rely on title alone (remove X, expand chevron, Pipette) in PaletteInputPanel.tsx and SimpleColorPicker.tsx. title is not a reliable accessible name — add aria-label. The anchor <select> and value <input> do correctly use aria-label, so just mirror that on the buttons. Fix this →
• Unlabelled text inputs: the palette-name input (PaletteInputPanel.tsx:126, placeholder only) and the hex input in SimpleColorPicker.tsx:17 have no <label>/aria-label.
• Good: the contrast badges encode the level as text (AA/FAIL/DECO), not colour alone. 👍

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🟢 Minor / nits

• ContrastTestPanel.tsx:22 — const stablePalettes = useMemo(() => palettes, [palettes]) is a no-op (returns the same reference with itself as the only dep); it stabilises nothing. Drop it and use palettes directly.
• next.config.ts /themebuilder → / redirect is a reasonable temporary shim; consider a follow-up to update the Share button to emit / directly so the redirect can be removed.
• On the two open questions in the description: discard the lockfile churn only after resolving the package.json downgrade above (they're linked). The plan/*.prompt.md docs are a judgement call — I'd leave build-agent prompt scratch files out of the app unless the team wants them tracked.

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Nice work on the restructure and the anchor-exact-color fix. The dependency downgrade is the one thing I'd resolve before merge; the rest are app-quality polish you can take or leave.
· feat/color-palette-generator-updates