fix(threads): move runtime import required for Thread.permissions_for

[shiftinv]

Summary

Fixes #1123.

In the future, we should look into enabling https://docs.astral.sh/ruff/rules/#flake8-type-checking-tch to catch these earlier. Historically those rules have been rather buggy, but they might be more mature now.

Checklist

• If code changes were made, then they have been tested
  • I have updated the documentation to reflect the changes
  • I have formatted the code properly by running pdm lint
  • I have type-checked the code by running pdm pyright
• This PR fixes an issue
• This PR adds something new (e.g. new method or parameters)
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)