chore: migrate test infrastructure from Jest to Vitest

[oliverlaz]

Summary

• Migrate test infrastructure from Jest to Vitest — replace Jest, Babel, and all related config with Vitest 4.x powered by the native Vite pipeline
• Rename JSX test files to .jsx — 111 test files + 19 snapshot files renamed so Vite handles JSX natively, eliminating the custom jsxInJs esbuild plugin
• Remove legacy example apps — delete capacitor, nextjs, and website-demos examples (keeping only vite and tutorial)
• Remove E2E/Ladle infrastructure — delete Playwright E2E tests, Ladle stories, and all related config
• Tidy ESLint config — migrate to flat config, remove Jest plugin, add Vitest plugin
• Restore Codecov integration — add the missing codecov/codecov-action upload step to CI
• Clean up unused dependencies — remove @axe-core/react, @types/dotenv, @types/uuid, @types/deep-equal, @types/moment, @types/textarea-caret, @types/lodash.defaultsdeep, autoprefixer, dotenv
• Update GitHub Actions — actions/checkout v4→v6, actions/setup-node v4→v6, actions/cache v4→v5

Details

Test migration:

• All jest.fn() / jest.spyOn() → vi.fn() / vi.spyOn()
• jest.mock() → vi.mock() with async importOriginal pattern
• Replaced jest.useFakeTimers() / jest.useRealTimers() with Vitest equivalents
• Updated timer advancing (jest.advanceTimersByTime → vi.advanceTimersByTime, etc.)
• Fixed mockImplementation() no-arg calls that behave differently in Vitest (→ mockResolvedValue())
• Setup file: jest.env.setup.js → vitest.setup.ts with @testing-library/jest-dom/vitest and vitest-axe
• Coverage: v8 provider scoped to src/**/*.{ts,tsx,js,jsx}, excludes @types, tests, mock-builders

JSX file rename:

• Renamed 111 .test.js → .test.jsx and 19 .test.js.snap → .test.jsx.snap
• Removed custom jsxInJs() esbuild pre-transform plugin from vitest.config.ts
• Vite now handles JSX natively via file extension — no double-transform overhead

Removed configs: .babelrc.js, babel.config.js, jest.config.js, jest-global-setup.js, assetsTransformer.js, playwright.config.ts, tsconfig.test.json (simplified)

Test plan

• yarn test — all unit tests pass with no unhandled errors
• yarn coverage — generates coverage report with correct file scoping
• yarn lint — no lint errors
• yarn types — TypeScript passes
• yarn build — build succeeds
• CI workflow runs tests and uploads coverage to Codecov

[github-actions]

Size Change: 0 B

Total Size: 442 kB

ℹ️ View Unchanged

Filename	Size
./dist/audioProcessing-BbOs2wMd.js	1.32 kB
./dist/cjs/emojis.js	2.96 kB
./dist/cjs/index.js	237 kB
./dist/cjs/mp3-encoder.js	1.27 kB
./dist/css/index.css	46.9 kB
./dist/css/v2/emoji-mart.css	1.84 kB
./dist/css/v2/emoji-replacement.css	300 B
./dist/css/v2/index.css	39.4 kB
./dist/css/v2/index.layout.css	22.8 kB
./dist/WithAudioPlayback-TERIQpZ6.js	88.3 kB

_{compressed-size-action}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.58%. Comparing base (a9feb11) to head (468295a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3047      +/-   ##
==========================================
- Coverage   80.31%   78.58%   -1.73%     
==========================================
  Files         561      428     -133     
  Lines       13098    12055    -1043     
  Branches     3413     3897     +484     
==========================================
- Hits        10520     9474    -1046     
- Misses       1912     2560     +648     
+ Partials      666       21     -645     

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