refactor Ord to be based on compare

aoc2024/Day13.newt

@@ -51,7 +51,7 @@ instance Sub BigInt where a - b = subbi a b
 instance Cast Int BigInt where cast x = itobi x
 instance Eq BigInt where a == b = jsEq a b
 instance Show BigInt where show = jsShow
-instance Ord BigInt where a < b = jsLT a b
+instance Ord BigInt where compare a b = jsCompare a b
 
 calcCost : BigInt → Machine → Maybe BigInt
 calcCost extra (MkMachine (ax, ay) (bx, by) (px, py)) =