Add Codecov setup with c8 coverage on unit tests

[JideEngDev]

Summary

• Adds c8 dev dependency — V8-native coverage tool that works seamlessly with ts-node
• Adds test:CI script: runs unit tests only (test/unit/*Spec.ts) with --reporter=json --reporter=lcov to generate coverage/lcov.info
• Adds codecov/codecov@5.0.3 orb to CircleCI config
• Adds a test job (runs before build) with codecov/upload uploading coverage/lcov.info
• Adds .codecov.yml with 80% patch coverage target and PR comments

Why unit tests only?

Integration tests (test/integration/) require live Trolley API credentials. Unit tests in test/unit/ run standalone with mocks and are safe to run in CI without secrets.

Test plan

• CircleCI test job runs npm run test:CI and passes
• coverage/lcov.info is generated
• Codecov receives the report and comments on this PR

Made with Cursor

[codecov]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

Thanks for integrating Codecov - We've got you covered ☂️