task-33: 网络错误走退避且不触发终态

8 个测试固化网络错误语义：fetch 拒绝不触发 onTerminal、不修改
taskStatuses、任务集合不丢失、onError 上报、失败后不立即自动重试
（退避）、恢复后继续轮询并正常触发终态。

行为由任务 31 的失败计数与既有 catch 路径实现，本次为验证型测试。

frontend-vue/tests/polling-network-error.test.ts

@@ -0,0 +1,134 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { useTaskProgressLoop } from '../src/shared/composables/useTaskProgressLoop.ts'
+
+function setupWindow() {
+  const storage = new Map<string, string>()
+  ;(globalThis as Record<string, unknown>).window = {
+    localStorage: {
+      getItem: (k: string) => storage.get(k) ?? null,
+      setItem: (k: string, v: string) => { storage.set(k, v) },
+      removeItem: (k: string) => { storage.delete(k) },
+    },
+    setTimeout: (fn: () => void, ms: number) => globalThis.setTimeout(fn, ms),
+    clearTimeout: (id: unknown) => globalThis.clearTimeout(id as number),
+    setInterval: (fn: () => void, ms: number) => globalThis.setInterval(fn, ms),
+    clearInterval: (id: unknown) => globalThis.clearInterval(id as number),
+  }
+}
+
+let scopeCounter = 0
+
+interface Harness {
+  loop: ReturnType<typeof useTaskProgressLoop<{ taskId?: number; status?: string }>>
+  terminalCalls: Array<{ taskId: number; status: string }>
+  errorCalls: unknown[]
+  fetchCalls: () => number
+}
+
+async function makeLoop(impl: () => Promise<{ items: unknown[] }>): Promise<Harness> {
+  const terminalCalls: Array<{ taskId: number; status: string }> = []
+  const errorCalls: unknown[] = []
+  let fetchCount = 0
+  const loop = useTaskProgressLoop<{ taskId?: number; status?: string }>({
+    scope: `net-err-${scopeCounter++}`,
+    fetchProgress: async (ids) => {
+      fetchCount += 1
+      return impl()
+    },
+    extractTaskId: (d) => d?.taskId,
+    extractStatus: (d) => d?.status,
+    getIntervalMs: () => 60000,
+    onTerminal: (taskId, _detail, status) => { terminalCalls.push({ taskId, status }) },
+    onError: (e) => { errorCalls.push(e) },
+  })
+  loop.reset([1, 2])
+  await new Promise<void>((r) => globalThis.setTimeout(r, 0))
+  return { loop, terminalCalls, errorCalls, fetchCalls: () => fetchCount }
+}
+
+test('test_network_error_no_terminal', async () => {
+  setupWindow()
+  const h = await makeLoop(async () => { throw new Error('network down') })
+  await h.loop.refreshOnce()
+  await h.loop.refreshOnce()
+  assert.equal(h.terminalCalls.length, 0, '网络错误不触发 onTerminal')
+  h.loop.dispose()
+})
+
+test('test_network_error_no_status_change', async () => {
+  setupWindow()
+  const h = await makeLoop(async () => { throw new Error('network down') })
+  await h.loop.refreshOnce()
+  assert.deepEqual(h.loop.taskStatuses.value, {}, '网络错误不修改 taskStatuses')
+  h.loop.dispose()
+})
+
+test('test_network_error_backoff_scheduled', async () => {
+  setupWindow()
+  const h = await makeLoop(async () => { throw new Error('network down') })
+  // 首轮自动刷新失败后：不立刻重试（下一轮按 60s 正常间隔调度），
+  // 短期内不应有新的 fetch 请求
+  const before = h.fetchCalls()
+  await new Promise<void>((r) => globalThis.setTimeout(r, 50))
+  assert.equal(h.fetchCalls(), before, '失败后进入退避，不立即自动重试')
+  h.loop.dispose()
+})
+
+test('test_network_error_on_error_called', async () => {
+  setupWindow()
+  const h = await makeLoop(async () => { throw new Error('network down') })
+  assert.equal(h.errorCalls.length, 1, 'onError 被调用')
+  assert.match((h.errorCalls[0] as Error).message, /network down/)
+  h.loop.dispose()
+})
+
+test('test_network_recovery', async () => {
+  setupWindow()
+  let fail = true
+  const h = await makeLoop(async () => {
+    if (fail) throw new Error('network down')
+    return { items: [{ taskId: 1, status: 'RUNNING' }] }
+  })
+  await h.loop.refreshOnce()
+  fail = false
+  await h.loop.refreshOnce()
+  assert.equal(h.loop.taskStatuses.value[1], 'RUNNING', '恢复后继续轮询并落地状态')
+  h.loop.dispose()
+})
+
+test('test_network_error_repeated', async () => {
+  setupWindow()
+  const h = await makeLoop(async () => { throw new Error('network down') })
+  for (let i = 0; i < 5; i++) {
+    await h.loop.refreshOnce()
+  }
+  assert.equal(h.errorCalls.length, 6, '多次失败仍退避上报')
+  assert.equal(h.terminalCalls.length, 0)
+  h.loop.dispose()
+})
+
+test('test_network_error_keeps_task', async () => {
+  setupWindow()
+  const h = await makeLoop(async () => { throw new Error('network down') })
+  await h.loop.refreshOnce()
+  assert.deepEqual(h.loop.taskIds.value, [1, 2], '任务不丢失')
+  h.loop.dispose()
+})
+
+test('test_network_error_then_success', async () => {
+  setupWindow()
+  let fail = true
+  const h = await makeLoop(async () => {
+    if (fail) throw new Error('network down')
+    return { items: [{ taskId: 1, status: 'SUCCESS' }] }
+  })
+  await h.loop.refreshOnce()
+  assert.equal(h.terminalCalls.length, 0, '网络错误阶段无终态回调')
+  fail = false
+  await h.loop.refreshOnce()
+  assert.equal(h.terminalCalls.length, 1, '恢复后成功响应正常触发终态')
+  assert.equal(h.terminalCalls[0].taskId, 1)
+  assert.equal(h.terminalCalls[0].status, 'SUCCESS')
+  h.loop.dispose()
+})