Refactor: Optimize block handling in optimizer

The optimizer now correctly handles empty blocks by collapsing them into
Nop nodes. It also unwraps blocks containing a single expression, making
the AST more concise. This change improves AST simplification by
ensuring that redundant block structures are removed.

src/ast/compiler/optimizer/engine.rs

@@ -562,10 +562,6 @@ impl Optimizer {
                     new_exprs.push(opt);
                 }
 
-                if !block_changed {
-                    return node_rc;
-                }
-
                 if self.enabled {
                     if new_exprs.is_empty() {
                         return Rc::new(folder.make_nop_node(node));
@@ -574,6 +570,10 @@ impl Optimizer {
                     }
                 }
 
+                if !block_changed {
+                    return node_rc;
+                }
+
                 (NodeKind::Block { exprs: new_exprs }, node.ty.clone())
             }