ci: configure pytest reporting for consumer tracking

[sammorley-short]

Configure pytest and mypy reporting in CI

Summary

Adds CI reporting artifacts for pytest and mypy to improve visibility into test results and code quality metrics. Reports are uploaded as GitHub Actions artifacts and retained for 14 days.

Changes

Pytest reporting & coverage (run_unit_tests job)

• Run pytest with JSON report (pytest-json-report) and coverage (pytest-cov) enabled.
• Upload pytest_report.json and htmlcov/ as artifacts per Python version matrix entry.

Mypy reporting (run_quality_checks job)

• Generate an HTML report from mypy via --html-report.
• Upload mypy-report/ as an artifact.

New dependencies (pyproject.toml)

• pytest-cov ^5.0.0 — coverage reporting for pytest.
• pytest-json-report ^1.5.0 — machine-readable JSON test reports.
• lxml ^6.0.2 — required by mypy's HTML report generation.

Coverage configuration (.coveragerc)

• Added .coveragerc to omit __init__.py files from coverage measurement.

Notes

• All report upload steps use if: always() so artifacts are available even when tests or type-checking fail.
• Artifact retention is set to 14 days.
• Minor whitespace cleanup in pyproject.toml (removed extraneous blank lines).