[Enhancement]: Add test coverage reporting to CI

[shauryagangrade]

Problem

The current CI pipeline runs tests but does not provide coverage reports. This makes it difficult to track test coverage over time and identify areas that need more tests.

Proposed solution

Add test coverage reporting to the CI pipeline:

• Use pytest-cov to generate coverage reports
• Set up coverage thresholds (e.g., 80% minimum)
• Publish coverage reports as GitHub Actions artifacts
• Add coverage badge to README
• Consider integrating with Codecov or Coveralls for historical tracking

Update the CI configuration to include:

- run: pip install pytest-cov
- run: pytest --cov=gcode --cov-report=xml --cov-report=html
- uses: actions/upload-artifact@v4
  with:
    name: coverage-report
    path: htmlcov/

Alternatives considered

• Using a different coverage tool
• Only tracking coverage locally
• Ignoring coverage metrics