fix(#1341): 修复智能剪辑封面生成的 3 个问题

A. generatingRef 卡死 → 改用 useState + 300秒超时保护
B. Step6 缺少进度弹窗 → 添加 Modal + Spin 进度提示
C. 预览视频 URL 没回写 → 预览完成后保存到 plan.config.rendered_storage_key

apps/web/src/api/template-editor/types.ts

@@ -118,6 +118,10 @@ export interface EditPlanConfig {
   generate_count?: number
   /** 素材模式 */
   material_mode?: string
+  /** 预览视频 URL（封面生成用） */
+  rendered_storage_key?: string
+  /** 生成任务 ID */
+  generation_task_id?: string
 }
 
 /* ── 模板草稿主体 ── */

apps/web/src/pages/generate/components/Step6CoverSettings.tsx

@@ -1,4 +1,5 @@
 import React from "react"
+import { Modal, Spin } from "antd"
 import type { CoverConfig } from "../../editing-planner/types"
 import { useStep6Cover } from "../hooks/useStep6Cover"
 import Button from "@/components/ui/Button"
@@ -18,6 +19,7 @@ interface Step6CoverSettingsProps {
 const Step6CoverSettings: React.FC<Step6CoverSettingsProps> = (props) => {
   const {
     coverSettings,
+    generating,
     generateAutoCover,
     showCoverSettings,
     setShowCoverSettings,
@@ -95,6 +97,14 @@ const Step6CoverSettings: React.FC<Step6CoverSettingsProps> = (props) => {
         template={editingTemplate}
         onSave={handleSaveTemplate}
       />
+
+      {/* AI 生成封面进度弹窗 */}
+      <Modal open={generating} closable={false} footer={null} centered>
+        <div style={{ textAlign: "center", padding: "24px 0" }}>
+          <Spin size="large" />
+          <p style={{ marginTop: 16, fontSize: 14, color: "#666" }}>AI 正在生成封面，请稍候...</p>
+        </div>
+      </Modal>
     </div>
   )
 }

apps/web/src/pages/generate/hooks/useStep4Preview.ts

@@ -4,6 +4,7 @@
  */
 import { useState, useCallback, useMemo, useEffect, useRef } from "react"
 import { createPreview, getPreviewStatus } from "@/api/generation"
+import { updateEditPlan } from "@/api/template-editor/editPlans"
 import type { PreviewTaskResponse, PreviewStatus as ApiPreviewStatus } from "@/api/generation"
 import type { EditingTemplate } from "@/api/editing-planner"
 import { safeExtractError } from "./generate-video/errorUtils"
@@ -250,6 +251,15 @@ export function useStep4Preview({
               it.index === index ? { ...it, status: "ready", result, progress: 100 } : it,
             ),
           )
+
+          // 保存预览视频 URL 到 plan config，供封面生成使用
+          if (result.videoUrl && selectedTemplate) {
+            updateEditPlan(selectedTemplate, {
+              config: { rendered_storage_key: result.videoUrl } as any,
+            }).catch((err) => {
+              console.warn("[Step4] 保存预览视频URL到plan config失败:", err)
+            })
+          }
           return
         }
 

apps/web/src/pages/generate/hooks/useStep6Cover.ts

@@ -30,7 +30,7 @@ export function useStep6Cover({
   assetIds = [],
   selectedTemplate = "",
 }: UseStep6CoverProps) {
-  const generatingRef = useRef(false)
+  const [generating, setGenerating] = useState(false)
 
   // ── 封面设置弹窗状态 ──
   const [showCoverSettings, setShowCoverSettings] = useState(false)
@@ -67,7 +67,7 @@ export function useStep6Cover({
 
   /** 调用后端智能封面 API，生成封面并更新预览 */
   const generateAutoCover = useCallback(async () => {
-    if (generatingRef.current) {
+    if (generating) {
       message.warning("封面正在生成中，请稍候...")
       return
     }
@@ -82,12 +82,17 @@ export function useStep6Cover({
       return
     }
 
-    generatingRef.current = true
+    setGenerating(true)
+    // 超时保护：300 秒后强制重置，防止 state 卡死导致按钮永久失效
+    const timeoutId = setTimeout(() => {
+      setGenerating(false)
+    }, 300000)
     try {
       const response = await generateCover(selectedTemplate, {
         asset_ids: assetIds,
         cover_type: "ai_frame",
       })
+      clearTimeout(timeoutId)
       const thumbnailUrl = response.cover?.image_url || ""
       if (thumbnailUrl) {
         onCoverSettingsChange({
@@ -100,12 +105,14 @@ export function useStep6Cover({
         message.warning("封面生成未返回图片，请重试")
       }
     } catch (err) {
+      clearTimeout(timeoutId)
       console.warn("[Step6] 智能封面生成失败:", err)
       message.error("封面生成失败，请稍后重试")
     } finally {
-      generatingRef.current = false
+      clearTimeout(timeoutId)
+      setGenerating(false)
     }
-  }, [selectedTemplate, assetIds, coverSettings, onCoverSettingsChange])
+  }, [selectedTemplate, assetIds, coverSettings, onCoverSettingsChange, generating])
 
   // ── 模板操作方法 ──
   const handleSelectTemplate = useCallback((id: string) => {
@@ -165,6 +172,7 @@ export function useStep6Cover({
 
   return {
     coverSettings,
+    generating,
     generateAutoCover,
     totalDuration,
     showCoverSettings,