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/compiler/lambda_collector.rs

@@ -32,10 +32,10 @@ impl<'a> LambdaCollector<'a> {
 
             BoundKind::Set { addr, value } => {
                 // Also track assignments to globals if they hold lambdas.
-                if let Address::Global(global_index) = addr {
-                    if let BoundKind::Lambda { .. } = &value.kind {
-                        self.registry.insert(*global_index, (**value).clone());
-                    }
+                if let Address::Global(global_index) = addr 
+                    && let BoundKind::Lambda { .. } = &value.kind 
+                {
+                    self.registry.insert(*global_index, (**value).clone());
                 }
                 self.visit(value);
             }