Refactor multiple if let bindings

Replaces nested `if let` statements with sequential `if let` bindings,
improving readability. This change is applied to `Dumper::log_bound`,
`LambdaCollector::visit_bound`, `Environment::call_object_method`, and
`Environment::call_lambda`.

src/ast/environment.rs

@@ -233,11 +233,11 @@ impl Environment {
         let mut vm = VM::new(self.global_values.clone());
         let result = vm.run(node)?;
         
-        if let Value::Object(obj) = &result {
-            if let Some(closure) = obj.as_any().downcast_ref::<crate::ast::vm::Closure>() {
-                // Execute the script body
-                return vm.run(&closure.function_node);
-            }
+        if let Value::Object(obj) = &result 
+            && let Some(closure) = obj.as_any().downcast_ref::<crate::ast::vm::Closure>() 
+        {
+            // Execute the script body
+            return vm.run(&closure.function_node);
         }
         
         Ok(result)
@@ -267,10 +267,10 @@ impl Environment {
         let mut result = vm.run_with_observer(&mut observer, &linked);
         
         // If result is a closure (script entry), execute the body too
-        if let Ok(Value::Object(obj)) = &result {
-            if let Some(closure) = obj.as_any().downcast_ref::<crate::ast::vm::Closure>() {
-                result = vm.run_with_observer(&mut observer, &closure.function_node);
-            }
+        if let Ok(Value::Object(obj)) = &result 
+            && let Some(closure) = obj.as_any().downcast_ref::<crate::ast::vm::Closure>() 
+        {
+            result = vm.run_with_observer(&mut observer, &closure.function_node);
         }
 
         Ok((result, observer.logs))