refactor: 字符串值改用 JsString 指针表示，键与字面量改用 PermInterner

crates/oxide_vm/tests/builtins_boolean_tests.rs

@@ -14,10 +14,7 @@ fn eval(vm: &mut Vm, source: &str) -> Result<JsValue, String> {
 }
 
 fn str_val(vm: &Vm, val: JsValue) -> String {
-    vm.kernel_core()
-        .string_forge()
-        .lookup(val.as_string_index())
-        .unwrap_or_default()
+    vm.lookup_str(val).unwrap_or_default()
 }
 
 // -- direct native fn tests --
@@ -47,7 +44,7 @@ fn tboolean_call_true_false() {
 #[test]
 fn tboolean_call_empty_string() {
     let mut vm = Vm::new();
-    let empty = vm.intern("");
+    let empty = vm.new_string("");
     assert!(!bool_ctor_call(&mut vm, empty).as_bool());
 }