Tons of details I'm omitting here, but basically Godot navmesh system designed for top-down games repurposed for side-scrollers, taught AI when to jump and drop, and adjusted the level to hide imperfections and edge cases. If the AI breaks for whatever reason, they just go left or right until they get unstuck. Also some AI has different goals and priorities and I think it helps make them more unpredictable in a fun way - having allies near you is not a guaranteed win.
Thanks for your review!