Add code coverage reporting with Codecov integration

[bartveneman]

Summary

This PR adds code coverage tracking and reporting to the project by integrating Codecov into the CI/CD pipeline and configuring Vitest to generate coverage reports.

Key Changes

• CI/CD Integration: Added Codecov upload step to the GitHub Actions test workflow with proper token authentication
• Coverage Configuration: Updated the test script to generate coverage reports using Vitest's coverage plugin (@vitest/coverage-v8)
• Dependencies: Added @vitest/coverage-v8 for coverage generation and @types/node for type support
• Environment Setup: Added CODECOV_TOKEN environment variable to the test job for secure token handling
• Gitignore: Added coverage/ directory to ignore generated coverage reports

Implementation Details

• Coverage reports are generated automatically when running npm test via the --coverage flag
• The Codecov action uses the token from GitHub secrets for secure authentication
• Coverage artifacts are excluded from version control to keep the repository clean

https://claude.ai/code/session_01KTr94r7gkrEYepWTgHT6Es

[codecov-commenter]

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 ☂️