Expose native implementation identity for verified host fast paths

crates/objects/src/README.md

@@ -8,7 +8,7 @@
 | [object.rs](object.rs) | Value、CompareOp、ObjectPayload（含显式函数标记）、ObjectHeader、EndorObject、Record、可发布数量元数据的 NativeFunction |
 | [types.rs](types.rs) | 托管名义类型、显式 Object/Type 引导、继承查询、受管方法表／接收者绑定、类字段、显式/类型化Trait定义、强类型签名边与声明约束、实例方法遮蔽检查和宿主缓存依赖名、原生构造委托、统一源码/原生/绑定方法参数区间和已知效果查询与能力验证、声明环境托管边、字段构造／写入检查与标记为校验读取的注解解析／匹配 |
 | [contracts.rs](contracts.rs) | 方法参数逆变/返回协变、名义/能力/联合包含关系、祖先方法更新的后代检查、动态注解调用前复查、类型化能力替换/返回约束与临时递归验证集合 |
-| [native.rs](native.rs) | NativeContext、CallArity/CallSignature 类型、Delegated/固定效果元数据、调用前检查、签名类型强边、上下文原生函数、作用域语言函数工厂、显式能力声明入口、函数标记、根与非递归委托调用 |
+| [native.rs](native.rs) | NativeContext、CallArity/CallSignature 类型、Delegated/固定效果元数据、调用前检查、签名类型强边、上下文原生函数与具体实现借用查询、作用域语言函数工厂、显式能力声明入口、函数标记、根与非递归委托调用 |
 | [effects.rs](effects.rs) | 非递归只读调用图证明、当前全局/闭包/绑定接收者解析、控制流栈事实合并，无执行或隐藏强根 |
 | [changes.rs](changes.rs) | 合并变更批次、变更键与有界通知额度 |
 | [number.rs](number.rs) | Integer／Decimal／Rational／BinaryFloat／Complex 的无损表示和装箱载荷 |

crates/objects/src/native.rs

@@ -222,7 +222,7 @@ impl CallSignature {
     }
 }
 
-pub trait NativeCallable: fmt::Debug + Send + Sync + 'static {
+pub trait NativeCallable: fmt::Debug + Send + Sync + std::any::Any {
     /// Immutable resolved types; referenced definitions must be traced by the
     /// payload. ContextNativeFunction snapshots and traces them automatically.
     fn signature(&self) -> Option<CallSignature> {
@@ -453,6 +453,14 @@ pub struct ContextNativeFunction {
 }
 
 impl ContextNativeFunction {
+    /// Borrow the concrete host implementation for intrinsic dispatch checks.
+    /// Function identity or a mutable class-table slot alone is not proof that
+    /// its current payload still implements a host intrinsic.
+    pub fn implementation<T: NativeCallable>(&self) -> Option<&T> {
+        let implementation: &dyn std::any::Any = self.callable.as_ref();
+        implementation.downcast_ref()
+    }
+
     pub fn new(
         name: &'static str,
         callable: impl NativeCallable,