Add pyrefly to CI

[MarcoGorelli]

Motivation

I'd discussed this with @yangdanny97 about adding type-checking using Pyrefly

Have you read the Contributing Guidelines on pull requests?

Yes/No

Test Plan

(How should this PR be tested? Do you require special setup to run the test or repro the fixed bug?)

Fixes

What issue does this PR fix? Use https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue to link this PR to a corresponding issue.

Fixes #<issue_number>

Related PRs

(Is this PR part of a group of changes? Link the other relevant PRs.)

[MarcoGorelli]

ci is failing with errors like

nox > [2026-03-09 11:33:18,356] python -m pip install -r requirements/dev.txt -e .
nox > [2026-03-09 11:33:20,262] Command python -m pip install -r requirements/dev.txt -e . failed with exit code 1:
nox > [2026-03-09 11:33:20,262] Obtaining file:///home/circleci/project
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Checking if build backend supports build_editable: started
  Checking if build backend supports build_editable: finished with status 'done'
  Getting requirements to build editable: started
  Getting requirements to build editable: finished with status 'error'
  error: subprocess-exited-with-error
  
  × Getting requirements to build editable did not run successfully.
  │ exit code: 1
  ╰─> [19 lines of output]
      Traceback (most recent call last):
        File "/home/circleci/project/.nox/coverage-3-10/lib/python3.10/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 389, in <module>
          main()
        File "/home/circleci/project/.nox/coverage-3-10/lib/python3.10/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 373, in main
          json_out["return_val"] = hook(**hook_input["kwargs"])
        File "/home/circleci/project/.nox/coverage-3-10/lib/python3.10/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 157, in get_requires_for_build_editable
          return hook(config_settings)
        File "/tmp/pip-build-env-llutku5m/overlay/lib/python3.10/site-packages/setuptools/build_meta.py", line 481, in get_requires_for_build_editable
          return self.get_requires_for_build_wheel(config_settings)
        File "/tmp/pip-build-env-llutku5m/overlay/lib/python3.10/site-packages/setuptools/build_meta.py", line 333, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=[])
        File "/tmp/pip-build-env-llutku5m/overlay/lib/python3.10/site-packages/setuptools/build_meta.py", line 301, in _get_build_requires
          self.run_setup()
        File "/tmp/pip-build-env-llutku5m/overlay/lib/python3.10/site-packages/setuptools/build_meta.py", line 520, in run_setup
          super().run_setup(setup_script=setup_script)
        File "/tmp/pip-build-env-llutku5m/overlay/lib/python3.10/site-packages/setuptools/build_meta.py", line 317, in run_setup
          exec(code, locals())
        File "<string>", line 14, in <module>
      ModuleNotFoundError: No module named 'pkg_resources'
      [end of output]

which seem unrelated to this PR?