Fix parseFlags to handle constant-folded flag values

When the compiler constant-folds `Pattern.CASE_INSENSITIVE | Pattern.COMMENTS`
into a single IntConstant (e.g. 6), parseFlags failed to match. This adds a
case to decompose the constant back into individual flag bits.

See scala/scala3#25731

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

oolong-core/src/main/scala/oolong/Utils.scala

@@ -143,6 +143,8 @@ private[oolong] object Utils:
               parseFlagsRec(term)(flags :+ mapNameToFlag(flag))
             case Select(term, "|")              => parseFlagsRec(term)(flags)
             case Select(Ident("Pattern"), flag) => flags :+ mapNameToFlag(flag)
+            case Literal(IntConstant(n)) =>
+              flags ++ (0 until 30).map(1 << _).filter(b => (n & b) != 0)
 
         parseFlagsRec(term)(List.empty)