fix: pending_length_exception 登记 GC 根遍历与搬移重写

crates/oxide_vm/src/session_gc/tests.rs

@@ -40,6 +40,17 @@ fn uncaught_value_is_gc_root() {
     assert!(has_ptr(&roots, session));
 }
 
+#[test]
+fn pending_length_exception_is_gc_root() {
+    let mut vm = Vm::new();
+    let obj = plain_object(&mut vm);
+    let session = vm.promote_object(obj);
+    vm.pending_length_exception = Some(JsValue::from_js_object(session));
+    let mut roots = Vec::new();
+    vm.for_each_root(|v| roots.push(v));
+    assert!(has_ptr(&roots, session));
+}
+
 #[test]
 fn suspended_signal_fields_are_roots() {
     let mut vm = Vm::new();