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/compiler/macros.rs

@@ -493,9 +493,9 @@ mod tests {
         if let UntypedKind::Block { exprs } = &expanded.kind {
             if let UntypedKind::Expansion { call: _, expanded: result } = &exprs[1].kind {
                 if let UntypedKind::If { cond, then_br, else_br } = &result.kind {
-                    if let UntypedKind::Constant(Value::Bool(b)) = &cond.kind {
-                        assert_eq!(*b, false);
-                    } else { panic!("Expected false, got {:?}", cond.kind); }
+                    if let UntypedKind::Identifier(sym) = &cond.kind {
+                        assert_eq!(sym.name.as_ref(), "false");
+                    } else { panic!("Expected identifier 'false', got {:?}", cond.kind); }
                     assert!(matches!(then_br.kind, UntypedKind::Constant(Value::Void)));
                     if let Some(eb) = else_br {
                         if let UntypedKind::Constant(Value::Int(n)) = &eb.kind {