fix(electron): offload chart plugin compute to worker

apps/desktop/preload/apis/chat.ts

@@ -78,6 +78,13 @@ export const chatApi = {
   ): Promise<{ success: boolean; newMessageCount: number; error?: string }> =>
     ipcRenderer.invoke('chat:incrementalImport', sessionId, filePath),
 
+  /**
+   * 图表插件计算会处理大量消息数组，Electron 下必须卸载到 worker，
+   * 避免 renderer 主线程同步执行造成窗口卡顿。
+   */
+  pluginCompute: <T = unknown>(fnString: string, input: unknown): Promise<T> =>
+    ipcRenderer.invoke('chat:pluginCompute', fnString, input),
+
   // ==================== Demo ====================
 
   importDemo: (