gh-133403: Add type annotations to generate_levenshtein_examples.py

[sandole]

Summary

• Added type annotations to Tools/build/generate_levenshtein_examples.py
• Updated Tools/build/mypy.ini to include the file for strict type checking
• Updated .github/workflows/mypy.yml to check the file in CI

Type annotations added

• Function parameters and return types for _substitution_cost, levenshtein, and main
• Variable type annotation for the examples set
• Added from __future__ import annotations for cleaner syntax

Test plan

• Ran mypy --config-file=Tools/build/mypy.ini Tools/build/generate_levenshtein_examples.py
• All mypy strict checks pass with no issues

This continues the ongoing effort in #133403 to add type checking to more build tools.

• Issue: Add typing to more build tools #133403

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📚 Documentation preview 📚: https://cpython-previews--143317.org.readthedocs.build/

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[JelleZijlstra]

I'm not sure we're OK with adding typing to arbitrary files. I'd prefer to get an approval from someone who works on this file.

[AA-Turner]

I'd agree with Jelle, I also think we should weigh up churn cost for PRs in this category. This PR doesn't seem to be LLM generated at first glance, but I imagine this ('add type hints to X file') could be a magnet for such activity.

A

[sandole]

sorry guys first time contributor here but would really like to be a regular contributor

who's the go-to guy for these CI / tooling changes?

[picnixz]

That would be any of the maintainer working on traceback.py. The original author's @ambv, but considering we actually didn't change this file since 2022, I think we won't ever have a change to change it in the future either.

Also, please avoid updating the branch if the CI is still green. It wastes CI resources as mentioned in https://devguide.python.org/getting-started/pull-request-lifecycle/#update-branch-button (more generally, please read the devguide).