Add CI/CD pipeline (build, lint, test)

[vayungodara]

Problem

No automated CI/CD — the only GitHub Actions are Claude code review. No build verification, linting, or test runs on PRs or pushes.

What to change

• Create .github/workflows/ci.yml with a workflow that runs on push to main and on pull requests
• Steps: checkout, install deps (npm ci), run lint (npm run lint), run build (npm run build), run tests (npm test)
• Use Node.js 18+ matrix
• Add status badges to README.md

Impact

Prevents broken builds from reaching main. Catches lint errors and test failures before merge.

Effort

~1-2 hours

[vayungodara]

Closing as duplicate — kept the more detailed version.

[vayungodara]

Closing as duplicate of #19