Shallow arcs are essentially segments but the cutoff is not clear. So we build a two-tiered system where we know that arcs with at least a sagitta-chord ratio of 0.3 are valid and we know that less than 0.2 is invalid. After that, we do additional rational checks to find problematic arcs that are more computationally intensive Fixes https://gitlab.com/kicad/code/kicad/-/issues/22475