build: test and fix pyproject classifiers

[psychedelicious]

Summary

• Fix invalid PyPI project classifiers which are preventing publishing to PyPI
• Add a script to check them
• Run the check in the build script
• Run the check in CI

Related Issues / Discussions

See failing publish here https://github.com/invoke-ai/InvokeAI/actions/runs/15266095813/job/42932344184

QA Instructions

n/a

Merge Plan

n/a

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)

[jazzhaiku]

@psychedelicious

Approved because code is very readable and this is a blocker.
But wondering why not use a TOML parser lib? e.g.
https://docs.python.org/3/library/tomllib.html

[psychedelicious]

Didn't know about that module. I had ChatGPT write the script, apparently it also didn't know about the module.

It looks like that module wasn't added to python's stdlib until v3.11. We technically support v3.10, so I'll leave the script as-is.