fix(ui): add 'use client' to chart components using React hooks

[bntvllnt]

Summary

• Adds "use client" to packages/ui/src/components/chart/area-chart.tsx and line-chart.tsx. Both components call useMemo/useState/useId, so without the directive they crash Next.js App Router consumers with TypeError: c.useState is not a function when imported into a Server Component tree (see Components using React hooks missing 'use client' directive — crashes Next.js RSC consumers #137).
• Adds a regression guard: packages/ui/scripts/check-use-client.ts scans every non-story/test .tsx under src/components/ and fails CI if any file referencing a React hook (useState, useEffect, useRef, useLayoutEffect, useCallback, useMemo, useReducer, useContext, useImperativeHandle, useId, useTransition, useDeferredValue, useSyncExternalStore, useInsertionEffect) is missing a leading "use client" directive.
• Wires the audit into .github/workflows/ci.yml as a new Quality Gates step (Check "use client" directives) and exposes it via pnpm -F @vllnt/ui check:use-client.

A repo-wide sweep confirmed those two chart files were the only remaining offenders; other components listed in the issue either don't exist in this repo or already carry the directive.

Base: feat/storybook

Test plan

• npx tsx scripts/check-use-client.ts from packages/ui — passes (OK: all 106 component file(s) with React hooks declare "use client".)
• Manual verification: confirm area-chart.tsx and line-chart.tsx both start with "use client"; and no other component under src/components/ uses a React hook without it.
• CI Quality Gates job runs the new Check "use client" directives step.
• Downstream smoke: import AreaChart/LineChart from @vllnt/ui into a Next.js 16 App Router Server Component page and confirm it renders without the useState is not a function crash.

Fixes #137

[vercel]

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Project	Deployment	Actions	Updated (UTC)
storybook	Ready	Preview, Comment	Apr 26, 2026 2:39pm
ui.vllnt.ai	Ready	Preview, Comment	Apr 26, 2026 2:39pm

[bntvllnt]

Status: ready for final human review.

Blockers: none.

What changed in this pass:

• pushed 5fe2a46 to merge the latest feat/storybook into this branch and clear the remaining PR conflict
• resolved the add/add conflict in packages/ui/src/components/client-directives.test.ts by keeping the branch helper/unit coverage and the base integration scan together
• confirmed PR fix(ui): add 'use client' to chart components using React hooks #144 is back to a clean merge state against feat/storybook

Validation summary:

• ✅ pnpm -F @vllnt/ui exec eslint scripts/check-use-client.ts src/components/client-directives.test.ts src/components/chart/area-chart.tsx src/components/chart/line-chart.tsx --max-warnings 0 --no-warn-ignored
• ✅ pnpm -F @vllnt/ui exec vitest run src/components/client-directives.test.ts (34 passed)
• ✅ pnpm -F @vllnt/ui exec tsx scripts/check-use-client.ts
• ✅ pnpm -F @vllnt/ui exec tsc --noEmit --project tsconfig.build.json
• ✅ pnpm -F @vllnt/ui build
• ✅ gh pr checks 144 (current Vercel preview checks passing on head 5fe2a46)

Claude review result:

• BLOCKING: none on the live narrowed diff vs feat/storybook
• WARN: low-priority follow-up only — CI calls npx tsx instead of the package script, the integration test skip list does not mirror the script's .spec.tsx exclusion, and hasUseClientDirective() still has an unusual mid-line */ parser edge case

Codex review result:

• attempted on the narrowed live diff, but Codex returned an account usage-limit error before it produced a review artifact

Action for bntvllnt:

• Final human review + merge decision on PR fix(ui): add 'use client' to chart components using React hooks #144 at head 5fe2a46 only. No further auto-fix is queued from this pass.