fix: 顶层 var 读写直连全局对象属性单一真值——GDI 序言 + 声明处同步删除，类原型 session 直分防晋升克隆 identity 分裂，自增减 int 保持

crates/oxide_vm/src/vm.rs

@@ -2040,6 +2040,16 @@ impl Vm {
                     self.dispatch_define_global_prop_c(a, key_idx)?;
                 }
 
+                OpCode::DEFINE_GLOBAL_PROP_IF_ABSENT => {
+                    self.dispatch_define_global_prop_if_absent(rd, a, b)?;
+                }
+
+                OpCode::DEFINE_GLOBAL_PROP_C_IF_ABSENT => {
+                    let key_idx = self.bytecode[self.pc] as u16;
+                    self.pc += 1;
+                    self.dispatch_define_global_prop_c_if_absent(a, key_idx)?;
+                }
+
                 OpCode::DEFINE_PROP_ATTRS => {
                     let attrs = self.bytecode[self.pc] as u8;
                     self.pc += 1;
@@ -2078,6 +2088,10 @@ impl Vm {
                     self.dispatch_new_object(rd, instr)?;
                 }
 
+                OpCode::NEW_SESSION_OBJECT => {
+                    self.dispatch_new_session_object(rd)?;
+                }
+
                 OpCode::CREATE_ARGUMENTS => {
                     self.dispatch_create_arguments(rd)?;
                 }