feat(title): add autoGenerateTitle for AI auto-select mode

apps/web/src/pages/generate/hooks/useStep4Title/useAiTitleGenerator.ts

@@ -72,9 +72,28 @@ export function useAiTitleGenerator({
     setAiTitleGenerating(false)
   }, [aiTitleInput])
 
+  /**
+   * 自动生成标题（供 AI 自动选择开关使用）
+   * 如果已有生成结果，直接从中选一个；否则用默认关键词生成
+   */
+  const autoGenerateTitle = useCallback((): string => {
+    if (aiTitleResults.length > 0) {
+      const picked = aiTitleResults[Math.floor(Math.random() * aiTitleResults.length)]
+      onTitleSettingsChange({ ...titleSettings, title: picked.title })
+      return picked.title
+    }
+    // 没有已有结果，用默认关键词生成
+    const results = generateTitlesFromTopic("短视频")
+    setAiTitleResults(results)
+    setHasGeneratedTitles(true)
+    const picked = results[Math.floor(Math.random() * results.length)]
+    onTitleSettingsChange({ ...titleSettings, title: picked.title })
+    return picked.title
+  }, [aiTitleResults, titleSettings, onTitleSettingsChange])
+
   const handleSelectAiTitle = useCallback(
     (title: string) => {
-      onTitleSettingsChange({ ...titleSettings, title, aiAutoSelect: false })
+      onTitleSettingsChange({ ...titleSettings, title })
       message.success("已选用此标题")
     },
     [titleSettings, onTitleSettingsChange],
@@ -98,5 +117,6 @@ export function useAiTitleGenerator({
     handleGenerateAiTitles,
     handleSelectAiTitle,
     handleRefreshAiTitles,
+    autoGenerateTitle,
   }
 }