feat(workflow): add node duplication

frontend/src/components/workflow/context.ts

@@ -2,7 +2,7 @@
 
 /**
  * 画布内共享上下文。GenericNode / ConditionEdge 由 ReactFlow 渲染,拿不到外层
- * 回调,统一通过这些 context 取节点规格与编辑/删除动作。
+ * 回调,统一通过这些 context 取节点规格与编辑/复制/删除动作。
  */
 
 import { createContext } from "react";
@@ -17,9 +17,14 @@ export type ElementActions = {
   remove: (id: string) => void;
 };
 
-const noop: ElementActions = { edit: () => {}, remove: () => {} };
+export type NodeActions = ElementActions & {
+  duplicate: (id: string) => void;
+};
 
-export const NodeActionContext = createContext<ElementActions>(noop);
+const noop: ElementActions = { edit: () => {}, remove: () => {} };
+const noopNodeActions: NodeActions = { ...noop, duplicate: () => {} };
+
+export const NodeActionContext = createContext<NodeActions>(noopNodeActions);
 export const EdgeActionContext = createContext<ElementActions>(noop);
 
 /** 调试通话中当前激活的节点 id(画布据此高亮),无激活为 null。 */