feat: 函数 length 属性（字节码函数/bind 包装器）+ getter/setter name 前缀

crates/oxide_ir/src/lower.rs

@@ -85,6 +85,7 @@ pub fn lower(f: &IRFunction) -> Result<CompiledModule, String> {
         is_arrow: f.is_arrow,
         captured_this_const_idx: f.captured_this_const_idx,
         function_name: f.function_name.clone(),
+        function_length: f.function_length,
         is_class_constructor: f.is_class_constructor,
         is_derived_constructor: f.is_derived_constructor,
         needs_home_object: f.needs_home_object,