fix(react-ui): stop false "unknown key" warnings for valid *ChartPalette theme keys

[ankit-thesys]

Fixes #714 · Linear: TH-2186

Summary

• Theming charts the typed way — createTheme({ defaultChartPalette: [...] }) on lightTheme/darkTheme — compiled fine but warned unknown key … It will be ignored twice per key on every dev boot. The message was false: the theme merge spreads user overrides wholesale, so palettes were reaching useTheme() and charts were applying them all along. Root cause: both validators derived their allow-list from Object.keys(defaultLightTheme), which defines none of the eight *ChartPalette keys declared on the Theme type (types-vs-runtime drift).
• Fix: one shared allow-list (KNOWN_THEME_KEYS = default theme keys + CHART_PALETTE_KEYS) consumed by both createTheme() and the ThemeProvider prop validator. CHART_PALETTE_KEYS is guarded by satisfies Record<keyof ChartColorPalette, true>, so adding/removing a palette key on the type without updating the allow-list is now a compile error. Deliberately no palette defaults in defaultTheme.ts — a default would shadow the per-chart theme prop fallback in useChartPalette, and themeToCssVars's string-only filter means palettes never belonged in CSS vars anyway.
• Added regression tests (ThemeProvider/__tests__/ThemeProvider.test.tsx) + tsconfig.test.json (required by the ESLint override for __tests__ files, mirroring react-headless). Updated the ThemeProvider AGENTS.md with the palette-key exception to the "adding a new token" recipe.

Investigation findings (verified against main)

Claim	Verdict
Type declares palette keys, validators reject them	Confirmed — but it's 8 keys (default/bar/line/area/pie/radar/radial/horizontalBar), not 5 as first reported
Both validators use Object.keys(defaultLightTheme)	Confirmed (ThemeProvider.tsx:112, utils.ts:70); consumers using createTheme got warned twice per key
"It will be ignored"	False — runtime probe through real ThemeProvider → useTheme() → useChartPalette showed palettes survive the merge ({ ...themes.dark, ...overrides }) and drive chart colors, incl. fallback to defaultChartPalette for unset chart types
Severity	Dev-only misleading noise — but it drove a downstream consumer to abandon theme-level palettes for per-chart customPalette workarounds

Is the problem gone?

Yes — re-ran the exact pre-fix reproduction probe against this branch:

	Before (main)	After (this PR)
Warnings on mount	6 (2 per palette key)	0
theme.barChartPalette in context	present	present (unchanged)
Chart colors from theme palette	applied	applied (unchanged)
Typo detection (defaultChartPalete)	warns	still warns, now suggests defaultChartPalette

Test plan

• pnpm --filter @openuidev/react-ui run test — 13/13 pass (7 new: allow-list covers every declared palette key + every default-theme key; createTheme silent for all 8 palette keys; ThemeProvider props silent for palette keys; genuine unknown keys still warn with suggestion; palettes flow theme → useTheme() → useChartPalette incl. defaultChartPalette fallback)
• pnpm --filter @openuidev/react-ui run typecheck — clean
• pnpm --filter @openuidev/react-ui run lint:check — 0 errors (pre-existing warnings only)
• pnpm --filter @openuidev/react-ui run format:check — clean
• Pre-fix repro probe re-run on branch: zero warnings, palettes still applied (table above)

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