Run tests and lint on pull requests

[ashrafee-dev]

Goal

Make CI provide feedback before changes are merged.

Acceptance criteria

• Trigger the workflow for both pushes and pull requests.
• Keep the existing Python 3.13 and uv sync --dev setup.
• Run the repository’s test and lint checks, or clearly explain why a check is separate.

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Maintainer source audit

.github/workflows/checks.yml runs pytest and pylint on both push and pull_request.

Verified against 9d8ac3e01df1 after #86 and #88. Closing the obsolete request so newcomers are not assigned already-resolved work. The original report above is preserved.