Selected/hovered contours can pass under normal ones.

[MewPurPur]

The draw calls are executed in order of the path commands. But that's wrong; instead, each color (selected/hovered/default) should have its lines/polylines saved in arrays for normal/selected/hovered and drawn at the end, first all normal ones, then all selected ones, then all hovered ones.

For a start, we could draw these as separate polylines, but ultimately it'll be a good idea to try to connect together lines into polylines as much as possible.