Add a handler for the spin-polarized Harris functional error

[Andrew-S-Rosen]

Summary

Closes #392. This is a non-fixable error, so we just warn the user to fix their INCAR. We don't make the change for them because it was probably a conceptual error.

Checklist

• Google format doc strings added. Check with ruff.
• Type annotations included. Check with mypy.
• Tests added for new features/fixes.
• If applicable, new classes/functions/modules have duecredit @due.dcite decorators to reference relevant papers by DOI (example)

Tip: Install pre-commit hooks to auto-check types and linting before every commit:

pip install -U pre-commit
pre-commit install

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.77%. Comparing base (aa02baf) to head (2d46225).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #402      +/-   ##
==========================================
+ Coverage   69.74%   69.77%   +0.02%     
==========================================
  Files          39       39              
  Lines        3504     3507       +3     
==========================================
+ Hits         2444     2447       +3     
  Misses       1060     1060              

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[shyuep]

Thanks!