fix: 脚本顶层 var/function 声明落 globalThis（DEFINE_GLOBAL_PROP 非可配置数据属性）

crates/oxide_ir/src/contract.rs

@@ -66,6 +66,7 @@ impl Inst {
             | OpCode::DELETE_PROP_DYNAMIC
             | OpCode::DEFINE_ACCESSOR
             | OpCode::DEFINE_PROP
+            | OpCode::DEFINE_GLOBAL_PROP
             | OpCode::SET_HOME_OBJECT
             // SPILL 写 VM spill 栈而非寄存器（恢复由 UNSPILL 写 rd）
             | OpCode::SPILL
@@ -231,11 +232,9 @@ impl Inst {
             // HALT：隐式读 reg 0（顶层返回值）
             OpCode::HALT => uses.push(0),
             // RETURN/THROW/YIELD/YIELD_STAR/AWAIT：读 rd（None→0）
-            OpCode::RETURN
-            | OpCode::THROW
-            | OpCode::YIELD
-            | OpCode::YIELD_STAR
-            | OpCode::AWAIT => push_operand(&mut uses, &self.rd),
+            OpCode::RETURN | OpCode::THROW | OpCode::YIELD | OpCode::YIELD_STAR | OpCode::AWAIT => {
+                push_operand(&mut uses, &self.rd)
+            }
             // 加载族：a 槽是 Const/Imm 立即数，无寄存器 use
             OpCode::LOAD_CONST
             | OpCode::CREATE_CLOSURE
@@ -264,7 +263,8 @@ impl Inst {
             | OpCode::SET_ELEM
             | OpCode::INIT_PRIVATE
             | OpCode::DEFINE_ACCESSOR
-            | OpCode::DEFINE_PROP => {
+            | OpCode::DEFINE_PROP
+            | OpCode::DEFINE_GLOBAL_PROP => {
                 push_operand(&mut uses, &self.rd);
                 push_operand(&mut uses, &self.a);
                 push_operand(&mut uses, &self.b);

crates/oxide_ir/src/inst.rs

@@ -197,6 +197,12 @@ impl Inst {
         Self::new(OpCode::DEFINE_PROP, target, value, key)
     }
 
+    /// 定义全局 var 绑定数据属性：target 为全局对象，value/key 为寄存器。
+    /// 属性可写/可枚举/不可配置（脚本顶层 var/function 声明的属性描述符）。
+    pub fn define_global_prop(target: Operand, value: Operand, key: Operand) -> Self {
+        Self::new(OpCode::DEFINE_GLOBAL_PROP, target, value, key)
+    }
+
     /// 静态删除属性：obj 同时放 rd/a 槽，const_idx 为属性名常量下标。
     pub fn delete_prop_static(obj: Operand, const_idx: u32) -> Self {
         Self::with_ext(OpCode::DELETE_PROP_STATIC, obj, obj, Operand::None, &[const_idx])