Add TypeScript unit tests and Cobertura coverage reporting with CI upload

[code-coverage-agent]

No test infrastructure existed; coverage reporting was impossible. This adds vitest-based unit tests and integrates Cobertura XML coverage into the CI pipeline.

Coverage configuration

• vitest.config.ts — V8 provider, Cobertura reporter output to coverage/ (gitignored)
• package.json — test → vitest run, test:coverage → vitest run --coverage

Unit tests (src/__tests__/)

• version.test.ts — VERSION_LATEST constant
• input.test.ts — validateArgs with latest, explicit semver, and invalid version strings
• config.test.ts — exportConfig env var exports and importConfig env var reads
• run.test.ts — CLIError shape, non-zero exit → CLIError, shell-operator injection → Error
• cli.test.ts — fillEnv sets/skips env vars based on arg presence

CI integration (.github/workflows/test.yml)

Augmented the existing lint job — tests already share the install/build steps:

- run: pnpm test:coverage
  shell: bash
- name: Upload coverage artifact
  if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository
  uses: actions/upload-artifact@v7
  with:
    name: coverage-report-typescript
    path: coverage/cobertura-coverage.xml

New upload-coverage-typescript job (elevated code-quality: write, fork-gated) downloads the artifact and calls actions/upload-code-coverage@v1.

ESLint

Added a test-file override in .eslintrc disabling import/first, import/order, and @typescript-eslint/require-await — required for vitest's vi.mock() hoisting pattern.