I suspect you don't need anything special for this. The GH API has support for reading comments from PRs. Maybe have it maintain a small local store to remember the IDs of the comments it's already read so it doesn't try to re-implement already-implemented fixes. Another similar thing you can do is a hook that reminds it to start a subagent to monitor the CI/autofix errors after it creates/updates a PR.

GitHub API is actually quite tricky here because there is a different between “comment” and “review” and “review comment” (paraphrasing, I don’t remember the details). So it’s not as simple as one API call that grabs the markdown. Of course you can write a creative one-liner to extract what you need, though.