wcc: reject final-band integer overflow; restore rewind columns

test/wcc/data/r989_intoverflow_dec_overflow/case.ww

@@ -1,7 +1,7 @@
 //ww:error "bad integer literal"
-// 989_intoverflow_reject dec_overflow: a 21-digit decimal exceeds u64.
+// Exact final-digit band: MAX/10 with 6 greater than MAX%10.
 package main;
 export fn main() i32 = {
-	let x: u64 = 99999999999999999999u64;
+	let x: u64 = 18446744073709551616u64;
 	return x: i32;
 };