refactor Ord to be based on compare

aoc2024/Day17.newt

@@ -21,7 +21,7 @@ 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
 
 data Machine : U where
   M : BigInt → BigInt → BigInt → List Int → Int → SnocList Int → Machine