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_number_tests.rs

@@ -76,11 +76,7 @@ fn number_constructor() {
 fn to_string_of_number() {
     let mut vm = Vm::new();
     let result = eval(&mut vm, "var n = 42; n.toString()").unwrap();
-    let s = vm
-        .kernel_core()
-        .string_forge()
-        .lookup(result.as_string_index())
-        .unwrap_or_default();
+    let s = vm.lookup_str(result).unwrap_or_default();
     assert_eq!(s, "42");
 }
 
@@ -88,11 +84,7 @@ fn to_string_of_number() {
 fn to_fixed_of_number() {
     let mut vm = Vm::new();
     let result = eval(&mut vm, "var n = 3.14159; n.toFixed(2)").unwrap();
-    let s = vm
-        .kernel_core()
-        .string_forge()
-        .lookup(result.as_string_index())
-        .unwrap_or_default();
+    let s = vm.lookup_str(result).unwrap_or_default();
     assert_eq!(s, "3.14");
 }
 
@@ -121,11 +113,7 @@ fn number_epsilon_is_positive() {
 fn number_to_exponential() {
     let mut vm = Vm::new();
     let result = eval(&mut vm, "var n = 123.456; n.toExponential(2)").unwrap();
-    let s = vm
-        .kernel_core()
-        .string_forge()
-        .lookup(result.as_string_index())
-        .unwrap_or_default();
+    let s = vm.lookup_str(result).unwrap_or_default();
     assert_eq!(s, "1.23e2");
 }
 
@@ -155,7 +143,7 @@ fn boxed_number_valueof_preserves_int_and_float() {
 fn boxed_number_is_object_and_call_stays_primitive() {
     let mut vm = Vm::new();
     let ty = eval(&mut vm, "typeof new Number(5)").unwrap();
-    assert_eq!(vm.kernel_core().string_forge().lookup(ty.as_string_index()).unwrap(), "object");
+    assert_eq!(vm.lookup_str(ty).unwrap(), "object");
 
     let n = eval(&mut vm, "Number('7')").unwrap();
     assert_eq!(n.as_int(), 7);