Migrate unit tests from Jest to Vitest

Replace Jest test runner with Vitest for native ES modules support
and faster test execution. This migration aligns the test tooling
with the Vite build system

Migrate unit tests from Jest to Vitest

Replace Jest test runner with Vitest for native ES modules support
and faster test execution. This migration aligns the test tooling
with the Vite build system and eliminates CommonJS compatibility
issues.

Why Vitest over Jest?

While Jest is a mature ecosystem with broader adoption (45.5k
GitHub stars vs Vitest's 15.7k), Vitest is the recommended testing
framework for Vue 3 + Vite projects:

1. **Native ESM Support**: Vitest runs tests directly as ESM
without transformation, while Jest requires Babel/transformation
layers that add complexity and slow down test execution.

2. **Vite Integration**: Shares the same configuration, plugins,
and resolvers as the Vite build system. This eliminates the
dual-config maintenance burden (vite.config.js + jest.config.js).

3. **Vue 3 Ecosystem Alignment**: Vitest is created by the Vue
team and is the official recommendation in Vue 3 documentation.
It has first-class Vue component testing support via
@vue/test-utils.

4. **Performance**: Cold start is significantly faster due to
Vite's on-demand compilation. HMR for tests provides instant
feedback during test-driven development.

5. **API Compatibility**: Vitest intentionally matches Jest's API,
making migration straightforward and allowing developers to
leverage existing Jest knowledge.

ESLint 9 Upgrade:
- Upgrade ESLint from 8.57.1 to 9.18.0
- Migrate from .eslintrc.cjs to eslint.config.js (flat config)
- Upgrade eslint-plugin-vue from 9.2.0 to 10.0.0
- Replace eslint-plugin-vitest with @vitest/eslint-plugin@1.1.43
- Replace @vue/eslint-config-prettier with eslint-config-prettier
- Add globals package for flat config environment definitions
- Update lint-staged from 13.0.3 to 16.0.0
- Update prettier from 3.2.5 to 3.4.2
- Disable stricter vue rules for follow-up PR:
vue/no-reserved-component-names, vue/no-unused-components,
vue/no-deprecated-delete-set, vue/no-required-prop-with-default

Pre-commit Hooks:
- Add simple-git-hooks and lint-staged for automatic linting
- Run eslint --fix on JS/Vue files before commit
- Run prettier --write on markdown files before commit
- Add .prettierrc.yaml matching CI configuration
- Include .cjs/.mjs files in prettier JS override

Documentation:
- Update unit testing guide for Vitest
- Update coding standards with pre-commit hook details

References:
- Vitest official comparison:
https://vitest.dev/guide/comparisons.html#jest
- Vue 3 testing guide:
https://vuejs.org/guide/scaling-up/testing.html#unit-testing
- Vite ecosystem recommendations:
https://vitejs.dev/guide/features.html#testing

Test Results:
- 19 test files, 123 tests passing
- No warnings or deprecation messages
- Test execution: ~3.1s (on par with Jest)

Changes:
- Replace jest.config.js with Vitest config in vite.config.js
- Create tests/vitest.setup.js with Vitest-compatible mocks
- Update package.json scripts for Vitest
- Add vue3-snapshot-serializer for cleaner snapshots
- Use happy-dom and real i18n instance for faster tests

Dependency Updates:
- Remove @vue/cli-plugin-unit-jest, @vue/vue3-jest, babel-jest,
jest
- Add vitest, @vitest/coverage-v8, jsdom, happy-dom,
vue3-snapshot-serializer

Test File Migrations:
- Replace jest.fn() with vi.fn()
- Replace jest.spyOn() with vi.spyOn()
- Replace jest.mock() with vi.mock()
- Replace jest.resetModules() with vi.resetModules()
- Replace jest.unmock() with vi.unmock()
- Replace require() with dynamic import() for ESM compatibility
- Add explicit Vitest imports (vi, describe, it, expect, etc.)

Snapshot Improvements:
- Use vue3-snapshot-serializer to strip data-v-* scoped style
attributes from snapshots for cleaner, more stable output
- Add SVG component stubs for logo assets to avoid verbose path
data in snapshots (logo-header.svg, login-company-logo.svg,
built-on-openbmc-logo.svg)
- Updated all snapshot files for Vitest format
- Removed obsolete Jest snapshot entries

Performance Optimizations:
- Use happy-dom instead of jsdom (17% faster environment setup)
- Use real i18n instance instead of mock (eliminates redundant
dynamic imports, 55% faster test execution)

Tested:
- npm run test:unit runs 19 test files, 123 tests, and passed
them all with 0 warnings.

Change-Id: Iaf04335db54a5ceeff09bcd43675a488828dc44f
Signed-off-by: Jason Westover <jwestover@nvidia.com>

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