You went through all of this work to make sure that you'd run your tests whenever you pushed a commit to a PR. You probably want to make sure that they actually stop someone from doing something silly, right?
In your repository's Settings > Branch > Branch protection rules, you can add some restrictions:
By default, this rule does not apply to administrators of the repository—which is probably you right now, but there is an additional option at the bottom that enforces this for administrators as well.