feat(workflow): add node duplication

frontend/src/components/workflow/WorkflowCanvas.tsx

@@ -328,6 +328,50 @@ export function WorkflowCanvas({
     [editingNodeId, nodes, onEditingNodeIdChange, setNodes, setEdges],
   );
 
+  const duplicateNode = useCallback(
+    (id: string) => {
+      const source = nodes.find((node) => node.id === id);
+      if (!source || source.type === "start") return;
+
+      const spec = specsByType[source.type as string];
+      if (!spec) return;
+      const limit = spec.constraints.maxInstances;
+      if (
+        limit !== undefined &&
+        nodes.filter((node) => node.type === source.type).length >= limit
+      ) {
+        return;
+      }
+
+      nodeSeq += 1;
+      const duplicateId = `${source.type}-${Date.now()}-${nodeSeq}`;
+      const sourceData = source.data as WorkflowNodeData;
+      const duplicateData = structuredClone(sourceData);
+      duplicateData.name = `${sourceData.name || spec.displayName}（副本）`;
+
+      setNodes((currentNodes) => [
+        ...currentNodes.map((node) => ({ ...node, selected: false })),
+        {
+          id: duplicateId,
+          type: source.type,
+          position: {
+            x: source.position.x + 40,
+            y: source.position.y + 40,
+          },
+          data: duplicateData,
+          selected: true,
+        },
+      ]);
+      onEditingNodeIdChange(null);
+    },
+    [
+      nodes,
+      onEditingNodeIdChange,
+      setNodes,
+      specsByType,
+    ],
+  );
+
   const handleNodesChange = useCallback(
     (changes: NodeChange[]) => {
       const startIds = new Set(
@@ -431,10 +475,12 @@ export function WorkflowCanvas({
         onEditingEdgeIdChange(null);
         onEditingNodeIdChange(id);
       },
+      duplicate: duplicateNode,
       remove: deleteNode,
     }),
     [
       deleteNode,
+      duplicateNode,
       onDebugOpenChange,
       onEditingEdgeIdChange,
       onEditingNodeIdChange,