fix(frontend): clean up voice preview listeners

frontend/src/components/workflow/WorkflowCanvas.tsx

@@ -176,6 +176,10 @@ export function WorkflowCanvas({
   const [addOpen, setAddOpen] = useState(false);
   const [addSourceId, setAddSourceId] = useState<string | null>(null);
   const [addPosition, setAddPosition] = useState<{ x: number; y: number } | null>(null);
+  // Fast Refresh 会替换模块级对象，而保留 React Flow 实例。用 state 固定本次
+  // 挂载使用的映射，避免热更新后被误判为每次渲染都在创建新对象。
+  const [flowNodeTypes] = useState(nodeTypes);
+  const [flowEdgeTypes] = useState(edgeTypes);
   const { screenToFlowPosition } = useReactFlow();
 
   // 只在可持久化的画布内容真正变化时回传。React Flow 挂载时会写入节点尺寸等
@@ -569,8 +573,8 @@ export function WorkflowCanvas({
               <ReactFlow
                 nodes={nodes}
                 edges={edges}
-                nodeTypes={nodeTypes}
-                edgeTypes={edgeTypes}
+                nodeTypes={flowNodeTypes}
+                edgeTypes={flowEdgeTypes}
                 onNodesChange={handleNodesChange}
                 onEdgesChange={onEdgesChange}
                 onConnect={onConnect}