Fix: Parse boolean literals as identifiers

Boolean literals `true` and `false` are now parsed as identifiers,
matching the behavior of other constants like `NaN`. This change aligns
the AST representation of boolean literals with their runtime constants.

src/ast/parser.rs

@@ -92,8 +92,6 @@ impl<'a> Parser<'a> {
             TokenKind::Identifier(id) => {
                 match id.as_ref() {
                     "..." => UntypedKind::Nop,
-                    "true" => UntypedKind::Constant(Value::Bool(true)),
-                    "false" => UntypedKind::Constant(Value::Bool(false)),
                     "void" => UntypedKind::Constant(Value::Void),
                     _ => UntypedKind::Identifier(id.into()),
                 }