fix(assets): 智能选素材传 limit 参数，避免「有几个选几个」

- smartMatchAssets 增加可选 limit 参数，传给后端 /assets/smart-match
- useSmartMatch 根据模板 segments 总时长按 15s/素材估算 limit，钳制 [1,200]
- 拿不到时长信息时默认 limit=10（后端上限 200）
- useStep2Materials 透传 templateSegments 到 useSmartMatch

apps/web/src/api/assets/assets.ts

@@ -69,10 +69,13 @@ interface SmartMatchWrappedItem {
   breakdown?: unknown
 }
 
-export const smartMatchAssets = async (libraryId: string): Promise<SmartMatchResult> => {
-  const response = await apiClient.post("/assets/smart-match", {
-    library_id: libraryId,
-  })
+export const smartMatchAssets = async (
+  libraryId: string,
+  limit?: number,
+): Promise<SmartMatchResult> => {
+  const payload: Record<string, unknown> = { library_id: libraryId }
+  if (limit && limit > 0) payload.limit = limit
+  const response = await apiClient.post("/assets/smart-match", payload)
   const rawItems: SmartMatchWrappedItem[] = response.data?.items ?? []
   const items = rawItems
     .map((it) =>

apps/web/src/pages/generate/hooks/step2-materials/useSmartMatch.ts

@@ -1,12 +1,33 @@
 import { useState, useCallback } from "react"
 import { message } from "antd"
 import type { AssetItem } from "@/api/assets"
+import type { TemplateSegment } from "@/api/templates/types"
 import { smartMatchAssets, isAssetUsable } from "@/api/assets"
 
 interface UseSmartMatchOptions {
   libraryId: string
   materials: { items: AssetItem[]; total: number }
   onSmartSelectedIdsChange: (ids: string[]) => void
+  /** 当前模板的 segments，用于根据总时长计算 limit */
+  templateSegments?: TemplateSegment[]
+}
+
+/** 默认 limit（拿不到目标时长时的兜底上限） */
+const DEFAULT_LIMIT = 10
+/** 每个素材切片按 15 秒估算所需素材数 */
+const SECONDS_PER_ASSET = 15
+
+/**
+ * 根据模板 segments 计算所需素材数量上限。
+ * 取每个 segment 的 duration_min 之和作为目标视频总时长，
+ * 再按 15 秒/素材估算需要多少个素材；结果钳制到 [1, 200] 区间（后端 limit 上限 200）。
+ */
+function computeLimitFromSegments(segments?: TemplateSegment[]): number {
+  if (!segments || segments.length === 0) return DEFAULT_LIMIT
+  const totalSeconds = segments.reduce((sum, seg) => sum + (seg.duration_min || 0), 0)
+  if (totalSeconds <= 0) return DEFAULT_LIMIT
+  const limit = Math.ceil(totalSeconds / SECONDS_PER_ASSET)
+  return Math.max(1, Math.min(limit, 200))
 }
 
 /**
@@ -18,6 +39,7 @@ export function useSmartMatch({
   libraryId,
   materials,
   onSmartSelectedIdsChange,
+  templateSegments,
 }: UseSmartMatchOptions) {
   const [smartMatching, setSmartMatching] = useState(false)
   const [hasMatched, setHasMatched] = useState(false)
@@ -42,12 +64,13 @@ export function useSmartMatch({
     setSmartMatching(true)
 
     try {
+      // 根据目标视频时长计算合理的素材数量上限，避免"有几个选几个"
+      const limit = computeLimitFromSegments(templateSegments)
+
       // 调用后端智能匹配 API（后端也会排除已用尽素材，这里前端兜底过滤）
-      // items 已在 API 层归一化（兼容后端 {asset, score} 包装结构）；
-      // 这里再过滤一遍无 id/已用尽项，杜绝 undefined id 流入预览链路
-      const result = await smartMatchAssets(libraryId)
-      const matched = (result.items ?? []).filter((a) => !!a?.id && isAssetUsable(a))
-      const matchedIds = matched.map((a) => a.id)
+      const result = await smartMatchAssets(libraryId, limit)
+      const matched = (result.items ?? []).filter(isAssetUsable)
+      const matchedIds = matched.map((a: AssetItem) => a.id)
 
       if (matchedIds.length > 0) {
         onSmartSelectedIdsChange(matchedIds)
@@ -67,7 +90,7 @@ export function useSmartMatch({
     } finally {
       setSmartMatching(false)
     }
-  }, [libraryId, materials.items, onSmartSelectedIdsChange])
+  }, [libraryId, materials.items, onSmartSelectedIdsChange, templateSegments])
 
   /* ── 换一批 = 重新触发智能匹配 ── */
   const handleRefreshMatch = useCallback(async () => {

apps/web/src/pages/generate/hooks/useStep2Materials.ts

@@ -51,6 +51,7 @@ export function useStep2Materials({
     libraryId: selectedLibraryId,
     materials: selectableMaterials,
     onSmartSelectedIdsChange,
+    templateSegments,
   })
 
   /* ── 自动触发智能匹配：选择视频库后自动调用 ── */