ci(actions): upgrade deprecated GitHub Actions

[stackia]

Summary

Upgrade the GitHub Actions used by CI and PyPI publishing:

• actions/checkout@v4 → actions/checkout@v7
• actions/setup-python@v5 → actions/setup-python@v7
• replace deprecated codecov/test-results-action@v1 with codecov/codecov-action@v7 and report_type: test_results
• upgrade the coverage upload from codecov/codecov-action@v5 to @v7

The updated actions and their relevant transitive actions/github-script@v8 dependency use Node.js 24. This removes the Node.js 20 deprecation annotations seen during the libdeye 2.1.6 release and the first validation run of this PR. The Python version, build commands, coverage behavior, and PyPI publishing configuration remain unchanged.

Validation

• Confirmed checkout v7, setup-python v7, and github-script v8 declare Node.js 24 runtimes
• Confirmed Codecov v7 supports report_type: test_results
• .venv/bin/pre-commit run --files .github/workflows/test.yml .github/workflows/publish.yml
• git diff --check
• PR CI exercises the updated actions directly

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.40%. Comparing base (9ff60ed) to head (9d6e67e).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #66   +/-   ##
=======================================
  Coverage   93.40%   93.40%           
=======================================
  Files           7        7           
  Lines         849      849           
  Branches       88       88           
=======================================
  Hits          793      793           
  Misses         25       25           
  Partials       31       31           

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