perf: track execution duration by state and bound summary I/O

src/preload/execution-stats.test.ts

@@ -12,10 +12,17 @@ vi.mock('electron', () => electron)
 it('reads execution statistics through the explicit typed bridge', async () => {
   await import('./index')
   const api = electron.contextBridge.exposeInMainWorld.mock.calls[0]![1] as DesktopApi
-  const summary = { durationMs: 1000, requestCount: 1, incompleteRequestCount: 0, activeRequestCount: 0, asOf: 2000, taskDurations: [{ id: 'task', durationMs: 1000, incompleteRequestCount: 0 }] }
+  const summary = { durationMs: 1000, runningCount: 0, incomplete: false, asOf: 2000, taskDurations: [{ id: 'task', durationMs: 1000, runningCount: 0, incomplete: false }] }
   electron.ipcRenderer.invoke.mockResolvedValue(summary)
   for (const scope of [{ conversationId: 'conversation' }, { projectId: 'project' }]) {
     expect(await api.tasks.getExecutionStats(scope)).toBe(summary)
     expect(electron.ipcRenderer.invoke).toHaveBeenLastCalledWith(ipcChannels.tasksExecutionStats, scope)
   }
+  const listener = vi.fn()
+  const unsubscribe = api.tasks.onExecutionStatsChanged(listener)
+  const handler = electron.ipcRenderer.on.mock.calls.find(([channel]) => channel === ipcChannels.tasksExecutionStatsChanged)![1]
+  handler()
+  expect(listener).toHaveBeenCalledOnce()
+  unsubscribe()
+  expect(electron.ipcRenderer.removeListener).toHaveBeenCalledWith(ipcChannels.tasksExecutionStatsChanged, handler)
 })

src/preload/index.ts

@@ -1273,6 +1273,11 @@ const desktopApi: DesktopApi = {
       ipcRenderer.invoke(ipcChannels.tasksList) as Promise<AssistantTask[]>,
     getExecutionStats: (input) =>
       ipcRenderer.invoke(ipcChannels.tasksExecutionStats, input) as Promise<ExecutionStats>,
+    onExecutionStatsChanged: (listener) => {
+      const handler = (): void => listener()
+      ipcRenderer.on(ipcChannels.tasksExecutionStatsChanged, handler)
+      return () => { ipcRenderer.removeListener(ipcChannels.tasksExecutionStatsChanged, handler) }
+    },
     setStatus: async (
       taskId: string,
       status: 'completed' | 'cancelled'