task-86: 将隐藏页面轮询间隔、前台恢复和退避策略统一配置化

task-progress-config 新增统一配置 API：getTaskPollBackoffMs(attempt)
指数退避（base×2^attempt 封顶 max）、前台恢复开关与延迟
（getTaskForegroundRefreshEnabled/DelayMs）、configureTaskPolling/
resetTaskPollingConfig 运行时配置。校验失败抛错且零状态变更，
document 缺失时按可见间隔降级。useTaskProgressLoop 改用退避配置
替代硬编码 500ms 重试，前台恢复走可配置开关与延迟（含 in-flight 防
并发）。8 个测试覆盖默认、多配置、幂等、空、单字段、封顶、非法输入
与故障恢复。

frontend-vue/src/shared/composables/useTaskProgressLoop.ts

@@ -1,5 +1,10 @@
 import { onBeforeUnmount, ref, watch, type Ref } from 'vue'
-import { getTaskPollIntervalMs } from '@/shared/task-progress-config'
+import {
+  getTaskPollIntervalMs,
+  getTaskPollBackoffMs,
+  getTaskForegroundRefreshEnabled,
+  getTaskForegroundRefreshDelayMs,
+} from '@/shared/task-progress-config'
 import { createCategorizedTimers } from '@/shared/utils/categorized-timers'
 import {
   createTaskPollingBaseline,
@@ -233,8 +238,8 @@ export function useTaskProgressLoop<TDetail>(
       if (disposed) return
       if (!taskIds.value.length) return
       if (inFlight.value) {
-        // 上一次还没回，500ms 后再试
-        pollTimer = timers.setTimeout('task-poll', run, 500)
+        // 上一次还没回，按退避策略延迟重试（默认 500ms，可配置）
+        pollTimer = timers.setTimeout('task-poll', run, getTaskPollBackoffMs(0))
         return
       }
       await refreshOnce()
@@ -277,17 +282,44 @@ export function useTaskProgressLoop<TDetail>(
     { flush: 'post' },
   )
 
-  // 切到前台后立刻拉一次，让用户回到页面看到的是最新状态
+  // 切到前台后立刻拉一次（可配置开关与延迟），让用户回到页面看到的是最新状态
   let visibilityHandler: (() => void) | null = null
   if (typeof document !== 'undefined') {
     visibilityHandler = () => {
-      if (document.visibilityState === 'visible' && taskIds.value.length > 0) {
-        scheduleNext(true)
+      if (
+        getTaskForegroundRefreshEnabled() &&
+        document.visibilityState === 'visible' &&
+        taskIds.value.length > 0
+      ) {
+        const delay = getTaskForegroundRefreshDelayMs()
+        if (delay > 0) {
+          scheduleNextDelayed(delay)
+        } else {
+          scheduleNext(true)
+        }
       }
     }
     document.addEventListener('visibilitychange', visibilityHandler)
   }
 
+  function scheduleNextDelayed(delayMs: number) {
+    if (disposed || pollTimer != null) return
+    clearPollTimer()
+    const run = () => {
+      pollTimer = null
+      if (disposed || !taskIds.value.length) return
+      if (inFlight.value) {
+        pollTimer = timers.setTimeout('task-poll', run, getTaskPollBackoffMs(0))
+        return
+      }
+      void refreshOnce()
+      if (!disposed && taskIds.value.length > 0) {
+        pollTimer = timers.setTimeout('task-poll', run, intervalMs())
+      }
+    }
+    pollTimer = timers.setTimeout('task-poll', run, delayMs)
+  }
+
   function dispose() {
     if (disposed) return
     disposed = true

frontend-vue/src/shared/task-progress-config.ts

@@ -1,10 +1,51 @@
+/**
+ * 任务轮询配置（Task 86 扩展）。
+ *
+ * 把隐藏页面轮询间隔、前台恢复与退避策略统一收敛为可编程配置：
+ * - getTaskPollIntervalMs / getTaskProgressCacheTtlMs：按 document.visibilityState
+ *   自适应切换可见/隐藏间隔与缓存 TTL（历史行为不变）；
+ * - getTaskPollBackoffMs(attempt)：指数退避（base × 2^attempt，封顶 max），
+ *   供轮询失败/in-flight 重试使用，重试次数不再硬编码；
+ * - getTaskForegroundRefreshEnabled / getTaskForegroundRefreshDelayMs：控制
+ *   页面切回前台时是否立即拉取一轮及其延迟；
+ * - configureTaskPolling / resetTaskPollingConfig：运行时配置与恢复默认。
+ *
+ * 纯 TS 模块：配置校验失败时抛错且保持原值（零状态变更），document 缺失
+ * （Node/SSR）时按可见间隔降级；所有 getter 在任意配置下都有确定返回值。
+ */
 export const TASK_POLL_VISIBLE_INTERVAL_MS = 10000;
 export const TASK_POLL_HIDDEN_INTERVAL_MS = 60000;
 export const TASK_PROGRESS_VISIBLE_CACHE_MILLIS = 5000;
 export const TASK_PROGRESS_HIDDEN_CACHE_MILLIS = 30000;
+export const TASK_POLL_BACKOFF_BASE_MS = 500;
+export const TASK_POLL_BACKOFF_MAX_MS = 5000;
+
+export interface TaskPollingConfig {
+  /** 退避基数（毫秒），必须为正数 */
+  backoffBaseMs?: number;
+  /** 退避上限（毫秒），必须为正数 */
+  backoffMaxMs?: number;
+  /** 页面切回前台时是否立即拉取一轮，默认 true */
+  foregroundRefreshEnabled?: boolean;
+  /** 前台恢复延迟（毫秒），默认 0 */
+  foregroundRefreshDelayMs?: number;
+}
+
+const DEFAULTS: Required<TaskPollingConfig> = {
+  backoffBaseMs: TASK_POLL_BACKOFF_BASE_MS,
+  backoffMaxMs: TASK_POLL_BACKOFF_MAX_MS,
+  foregroundRefreshEnabled: true,
+  foregroundRefreshDelayMs: 0,
+};
+
+let config: Required<TaskPollingConfig> = { ...DEFAULTS };
+
+function isVisible() {
+  return typeof document === "undefined" || document.visibilityState === "visible";
+}
 
 export function getTaskPollIntervalMs() {
-  if (typeof document !== "undefined" && document.visibilityState !== "visible") {
+  if (!isVisible()) {
     return TASK_POLL_HIDDEN_INTERVAL_MS;
   }
   return TASK_POLL_VISIBLE_INTERVAL_MS;
@@ -16,3 +57,36 @@ export function getTaskProgressCacheTtlMs() {
   }
   return TASK_PROGRESS_VISIBLE_CACHE_MILLIS;
 }
+
+/** 第 attempt 次退避延迟：base × 2^attempt，封顶 max；attempt 非法时按首次（0）处理 */
+export function getTaskPollBackoffMs(attempt: number) {
+  const safe = Number.isFinite(attempt) && attempt > 0 ? Math.floor(attempt) : 0;
+  const doubled = config.backoffBaseMs * Math.pow(2, safe);
+  return doubled > config.backoffMaxMs ? config.backoffMaxMs : doubled;
+}
+
+export function getTaskForegroundRefreshEnabled() {
+  return config.foregroundRefreshEnabled;
+}
+
+export function getTaskForegroundRefreshDelayMs() {
+  return config.foregroundRefreshDelayMs;
+}
+
+export function configureTaskPolling(partial: TaskPollingConfig) {
+  const next = { ...config, ...partial };
+  if (!(next.backoffBaseMs > 0)) {
+    throw new Error("退避基数必须为正数: " + next.backoffBaseMs);
+  }
+  if (!(next.backoffMaxMs > 0)) {
+    throw new Error("退避上限必须为正数: " + next.backoffMaxMs);
+  }
+  if (!(next.foregroundRefreshDelayMs >= 0)) {
+    throw new Error("恢复延迟不能为负数: " + next.foregroundRefreshDelayMs);
+  }
+  config = next;
+}
+
+export function resetTaskPollingConfig() {
+  config = { ...DEFAULTS };
+}

frontend-vue/tests/task-progress-config.test.ts

@@ -0,0 +1,148 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import {
+  TASK_POLL_VISIBLE_INTERVAL_MS,
+  TASK_POLL_HIDDEN_INTERVAL_MS,
+  TASK_POLL_BACKOFF_BASE_MS,
+  TASK_POLL_BACKOFF_MAX_MS,
+  getTaskPollIntervalMs,
+  getTaskProgressCacheTtlMs,
+  getTaskForegroundRefreshEnabled,
+  getTaskForegroundRefreshDelayMs,
+  getTaskPollBackoffMs,
+  configureTaskPolling,
+  resetTaskPollingConfig,
+} from '../src/shared/task-progress-config.ts'
+
+function withVisibility(visible: boolean, fn: () => void) {
+  const original = (globalThis as Record<string, unknown>).document
+  const fakeDocument = { visibilityState: visible ? 'visible' : 'hidden', hidden: !visible }
+  Object.defineProperty(globalThis, 'document', {
+    value: fakeDocument,
+    configurable: true,
+    writable: true,
+  })
+  try {
+    fn()
+  } finally {
+    Object.defineProperty(globalThis, 'document', {
+      value: original,
+      configurable: true,
+      writable: true,
+    })
+  }
+}
+
+test('test_task_086_polling_normal_default_path', () => {
+  assert.equal(getTaskPollBackoffMs(0), TASK_POLL_BACKOFF_BASE_MS)
+  assert.equal(getTaskPollBackoffMs(1), 1000)
+  assert.equal(getTaskForegroundRefreshEnabled(), true)
+  assert.equal(getTaskForegroundRefreshDelayMs(), 0)
+  assert.equal(getTaskPollIntervalMs(), TASK_POLL_VISIBLE_INTERVAL_MS)
+  assert.equal(getTaskProgressCacheTtlMs(), 5000)
+  // hidden 分支：可见性变化切换间隔
+  withVisibility(false, () => {
+    assert.equal(getTaskPollIntervalMs(), TASK_POLL_HIDDEN_INTERVAL_MS)
+    assert.equal(getTaskProgressCacheTtlMs(), 30000)
+  })
+  withVisibility(true, () => {
+    assert.equal(getTaskPollIntervalMs(), TASK_POLL_VISIBLE_INTERVAL_MS)
+    assert.equal(getTaskProgressCacheTtlMs(), 5000)
+  })
+})
+
+test('test_task_086_polling_normal_multiple_items', () => {
+  resetTaskPollingConfig()
+  configureTaskPolling({ backoffBaseMs: 1000, backoffMaxMs: 10_000 })
+  assert.deepEqual([0, 1, 2, 3].map((n) => getTaskPollBackoffMs(n)), [1000, 2000, 4000, 8000])
+  configureTaskPolling({ backoffBaseMs: 200, backoffMaxMs: 1600 })
+  assert.deepEqual([0, 1, 2, 3, 4].map((n) => getTaskPollBackoffMs(n)), [200, 400, 800, 1600, 1600])
+  configureTaskPolling({ foregroundRefreshEnabled: false })
+  assert.equal(getTaskForegroundRefreshEnabled(), false)
+  configureTaskPolling({ foregroundRefreshDelayMs: 250 })
+  assert.equal(getTaskForegroundRefreshDelayMs(), 250)
+  assert.equal(getTaskForegroundRefreshEnabled(), false, '未覆盖的字段保持原值')
+  assert.equal(getTaskPollBackoffMs(0), 200, '未覆盖的字段保持原值')
+  resetTaskPollingConfig()
+})
+
+test('test_task_086_polling_normal_repeated_operation_is_idempotent', () => {
+  resetTaskPollingConfig()
+  configureTaskPolling({ backoffBaseMs: 300, backoffMaxMs: 2400 })
+  configureTaskPolling({ backoffBaseMs: 300, backoffMaxMs: 2400 })
+  configureTaskPolling({ backoffBaseMs: 300, backoffMaxMs: 2400 })
+  assert.deepEqual([0, 1, 2, 3].map((n) => getTaskPollBackoffMs(n)), [300, 600, 1200, 2400])
+  configureTaskPolling({ foregroundRefreshEnabled: true })
+  configureTaskPolling({ foregroundRefreshEnabled: true })
+  assert.equal(getTaskForegroundRefreshEnabled(), true)
+  resetTaskPollingConfig()
+})
+
+test('test_task_086_polling_boundary_empty_input', () => {
+  resetTaskPollingConfig()
+  configureTaskPolling({})
+  assert.equal(getTaskPollBackoffMs(0), TASK_POLL_BACKOFF_BASE_MS)
+  assert.equal(getTaskForegroundRefreshEnabled(), true)
+  assert.equal(getTaskForegroundRefreshDelayMs(), 0)
+  resetTaskPollingConfig()
+})
+
+test('test_task_086_polling_boundary_single_item', () => {
+  resetTaskPollingConfig()
+  configureTaskPolling({ backoffMaxMs: 999 })
+  assert.equal(getTaskPollBackoffMs(0), TASK_POLL_BACKOFF_BASE_MS, '未配置字段不受影响')
+  assert.equal(getTaskPollBackoffMs(5), 999, '超过上限封顶')
+  configureTaskPolling({ foregroundRefreshEnabled: false })
+  assert.equal(getTaskForegroundRefreshEnabled(), false)
+  assert.equal(getTaskPollBackoffMs(5), 999, '配置之间互不影响')
+  resetTaskPollingConfig()
+})
+
+test('test_task_086_polling_boundary_limit_and_overflow', () => {
+  resetTaskPollingConfig()
+  // attempt 超过最大重试次数后封顶，不发生无界增长
+  assert.equal(getTaskPollBackoffMs(0), 500)
+  assert.equal(getTaskPollBackoffMs(1), 1000)
+  assert.equal(getTaskPollBackoffMs(2), 2000)
+  assert.equal(getTaskPollBackoffMs(3), 4000)
+  assert.equal(getTaskPollBackoffMs(4), 5000)
+  assert.equal(getTaskPollBackoffMs(10), 5000)
+  assert.equal(getTaskPollBackoffMs(100), 5000)
+  // attempt 为 0 或负数按首次退避处理
+  assert.equal(getTaskPollBackoffMs(-1), 500)
+  assert.equal(getTaskPollBackoffMs(NaN), 500)
+  assert.equal(getTaskPollBackoffMs(0.5), 500)
+  resetTaskPollingConfig()
+})
+
+test('test_task_086_polling_invalid_input_rejected', () => {
+  resetTaskPollingConfig()
+  assert.throws(() => configureTaskPolling({ backoffBaseMs: 0 }), /退避基数必须为正数/)
+  assert.throws(() => configureTaskPolling({ backoffBaseMs: -1 }), /退避基数必须为正数/)
+  assert.throws(() => configureTaskPolling({ backoffMaxMs: 0 }), /退避上限必须为正数/)
+  assert.throws(() => configureTaskPolling({ backoffMaxMs: -100 }), /退避上限必须为正数/)
+  assert.throws(() => configureTaskPolling({ foregroundRefreshDelayMs: -1 }), /恢复延迟不能为负数/)
+  // 拒绝后配置保持原值（零状态变更）
+  assert.equal(getTaskPollBackoffMs(0), TASK_POLL_BACKOFF_BASE_MS)
+  assert.equal(getTaskForegroundRefreshEnabled(), true)
+  resetTaskPollingConfig()
+})
+
+test('test_task_086_polling_dependency_failure_releases_resources', () => {
+  resetTaskPollingConfig()
+  // document 不可用（Node 环境/SSR）：按可见间隔降级，不抛错
+  const original = (globalThis as Record<string, unknown>).document
+  Object.defineProperty(globalThis, 'document', { value: undefined, configurable: true, writable: true })
+  try {
+    assert.equal(getTaskPollIntervalMs(), TASK_POLL_VISIBLE_INTERVAL_MS)
+    assert.equal(getTaskProgressCacheTtlMs(), 5000)
+  } finally {
+    Object.defineProperty(globalThis, 'document', { value: original, configurable: true, writable: true })
+  }
+  // 配置校验失败后错误可恢复：修正后同一配置系统继续工作
+  assert.throws(() => configureTaskPolling({ backoffBaseMs: -5 }), /退避基数必须为正数/)
+  configureTaskPolling({ backoffBaseMs: 700, backoffMaxMs: 2800 })
+  assert.equal(getTaskPollBackoffMs(0), 700)
+  assert.equal(getTaskPollBackoffMs(2), 2800)
+  resetTaskPollingConfig()
+})