Fix[CI]: Use correct Python version and enable coverage upload

[dkargatzis]

What’s Changed

• Replaced uv python install with actions/setup-python@v5 to correctly set the runner’s Python version (3.12).
• Updated pytest command to include --cov and --cov-report=xml, ensuring coverage is properly calculated and coverage.xml is generated.
• This resolves an issue where the Codecov step was silently failing due to the missing coverage file.

Why

Without these fixes:

• The CI may use the default Python version instead of the one defined in the matrix.
• The Upload coverage reports step would fail silently since no coverage.xml was produced.

[watchflow]

❌ Watchflow rules file not found

The file .watchflow/rules.yaml is missing from your repository.

How to fix:

1. Create a file at .watchflow/rules.yaml in your repository root.
2. Add your rules in the following format:

   rules:
     - id: example-rule
       description: Example rule description
       ...

3. Read the documentation for more details.

After adding the file, push your changes to re-run validation.

[dimeloper]

Just wondering, what is the plan for the code coverage reporting? My suggestion would be to upload the reports on https://about.codecov.io/ - then we can get test coverage analysis reports within our PRs, for free 😄

See an example:

[dkargatzis]

@dimeloper It looks like repo was already using your approach but had a few things missing. I've included the token configuration and created a codecov.yml to customize the reporting behavior.

Btw, the comment is posted as require_changes: yes in the config, so it only shows when there are actual coverage changes - that's why you don't see a comment on this PR since it's just CI fixes.