ci(dspy): Fix failing tests coming from forks

[isaacbmiller]

This PR does two main things:

1. It fixes an issue where the code would try to checkout code from a repo it did not have access to. The way I wrote it to checkout {{ github.head_ref}} was incorrect. This should resolve the issues that CI tests coming from forks face.
2. Starts to add a workflow to upload an artifact to add a comment to run the style checks

[isaacbmiller]

@okhat This should address everyones failing tests. The first runs may be longer as the cache rebuilds