Use pyrefly for type checking

[rchen152]

This PR switches the type checker for helion from pyright to pyrefly. Benefits of switching:

• Faster local type checking: in testing on my machine, a full check with pyright takes about 25s, while a full check with pyrefly takes <2s [1].
• Faster CI: the pre-commit step of lint.yml currently takes about 30s to run [2]; a run on this PR took only 16s [3].
• Fewer error suppressions: helion previously needed 405 # pyright: ignore directives; only 340 # pyrefly: ignore directives are needed.

The bulk of this PR is a mechanical removal of pyright suppressions and addition of pyrefly suppressions. The interesting changes are:

• rchen152@1528287 changes the type checker from pyright to pyrefly.
• rchen152@b718906 adds some type annotations to help pyrefly and removes some typing.cast calls that are no longer needed.
• rchen152@a085515 removes some search paths that pyright was using (?) that pyrefly can't find.

[oulgen]

also update agents.md

[oulgen]

can we use the pyrefly with the version in the config? i think @lolpack added something?

[rchen152]

I tried switching to the second option here that's supposed to let you specify the version, but I couldn't get it to work. Pyrefly starts producing a lot of import errors (on torch, triton, etc.) that suggest it's no longer able to find dependencies.

[rchen152]

I opened an issue against pyrefly-pre-commit: facebook/pyrefly-pre-commit#7.

[rchen152]

Woohoo! @oulgen thanks for the speedy review