Since writing this a tangentially related thing we've added, is a github action that runs on any PR that includes a (Rails) database migration, and reviews it, comparing it to our docs for how to write good migrations.
Claude helped write the action so it was super easy to set up.
It works particularly well for migrations because all the context is in the PR. We haven't had as much luck with reviewing general PRs where the reason for a change being good or bad could be outside the diff, and where there aren't as clearly defined rules for what should be avoided.
For Claude specifically, people who take more time to write long detailed prompts tend to get much better outcomes. Including me, since I made the effort to get better at prompt writing.