Bump version of pyright used in CI #26238

Hi! 👋 I noticed the version of pyright used in CI is over 3 years old:

Could we bump this to the latest version and fix any corresponding type check errors? There have been many improvements to pyright since then that would be nice to include, and it would harden the codebase.

(A separate but related issue is that the version of Python used in the check_types step, 3.10, is now EOL; we might want to bump that to 3.14 as well.)

I'm happy to submit a PR if there's interest.