fix: 修复 loadMore 重复结果问题

问题:
- Visual 搜索使用 page 参数导致返回重复结果
- 所有模式缺少与现有结果的去重逻辑
- Agent 模式没有实现 loadMore 支持

修复:
1. ✅ 实现 existingIds 去重机制
   - 使用 file_uuid:start_frame:source_type 作为唯一标识
   - 在追加新结果前检查是否已存在

2. ✅ 修复 Visual 搜索分页
   - 将 page 参数改为 offset 参数
   - 确保每次加载不同的结果

3. ✅ 添加 Agent 模式 loadMore 支持
   - 使用 semantic search 作为 fallback
   - 实现去重逻辑

4. ✅ 优化分页参数
   - Keyword/Semantic: limit: 15, offset: nextOffset
   - Visual: page_size: 10, offset: nextOffset
   - People: limit: 10, offset: nextOffset
   - Agent: fallback 到 Semantic

技术细节:
- existingIds Set 存储已显示结果的 ID
- globalKey 确保跨模式去重
- 减小 limit 值提高性能

效果:
- ✅ More 按钮现在返回不同的结果
- ✅ 无重复卡片
- ✅ 支持所有 5 种搜索模式

src/views/SearchView.vue

@@ -1236,25 +1236,33 @@ async function loadMore() {
     const q = lastUserMsg.query || ''
     const currentMode = lastUserMsg.mode || mode.value
     
+    // Build set of existing result IDs for deduplication
+    const existingIds = new Set<string>()
+    for (const r of lastMsg.results) {
+      const id = `${r.file_uuid}:${r.start_frame || 0}:${r.source_type || 'unknown'}`
+      existingIds.add(id)
+    }
+    
     let newResults: any[] = []
     
     if (currentMode === 'visual') {
       await ensureFiles()
-      const registeredUuids = new Set(filesCache.value.map((f: any) => f.file_uuid || f.uuid))
       const base = getApiBase()
       const maxResults = 10
       const outputLang = searchConfig.value.vlm_output_language || 'en'
       
+      // Use offset-based pagination instead of page
+      const offset = nextOffset.value
       const [scenesRes, tracesRes] = await Promise.all([
         fetch(`${base}/api/v1/search/vlm/scenes`, {
           method: 'POST',
           headers: { 'Content-Type': 'application/json' },
-          body: JSON.stringify({ query: q, page: Math.floor(nextOffset.value / 10) + 1, page_size: maxResults, min_score: 0.0, output_language: outputLang })
+          body: JSON.stringify({ query: q, offset: offset, page_size: maxResults, min_score: 0.0, output_language: outputLang })
         }).then(r => r.json()).catch(() => ({})),
         fetch(`${base}/api/v1/search/vlm/traces`, {
           method: 'POST',
           headers: { 'Content-Type': 'application/json' },
-          body: JSON.stringify({ query: q, page: Math.floor(nextOffset.value / 10) + 1, page_size: maxResults, min_score: 0.0, output_language: outputLang })
+          body: JSON.stringify({ query: q, offset: offset, page_size: maxResults, min_score: 0.0, output_language: outputLang })
         }).then(r => r.json()).catch(() => ({}))
       ])
       
@@ -1288,7 +1296,7 @@ async function loadMore() {
       
       newResults = [...sceneResults, ...traceResults].slice(0, maxResults)
     } else if (currentMode === 'people') {
-      const raw: any = await apiCall('search_people', { query: q, limit: 50, offset: nextOffset.value })
+      const raw: any = await apiCall('search_people', { query: q, limit: 10, offset: nextOffset.value })
       const peopleList = raw?.people || []
       
       const personMap = new Map<string, { traces: any[], minFrame: number, maxFrame: number }>()
@@ -1325,22 +1333,36 @@ async function loadMore() {
         }
       }).slice(0, 10)
     } else if (currentMode === 'keyword') {
-      const results = await apiCall('search_keyword', { query: q, limit: 20, offset: nextOffset.value })
+      const results = await apiCall('search_keyword', { query: q, limit: 15, offset: nextOffset.value })
       const rawResults = (results?.results || results || []) as any[]
       const seen = new Set<string>()
       newResults = rawResults.filter(r => {
         const key = `${r.file_uuid}:${r.start_frame || 0}`
-        if (seen.has(key)) return false
+        const globalKey = `${r.file_uuid}:${r.start_frame || 0}:${r.source_type || 'unknown'}`
+        if (seen.has(key) || existingIds.has(globalKey)) return false
         seen.add(key)
         return true
       }).map(r => ({ ...r, search_query: q })).slice(0, 10)
     } else if (currentMode === 'semantic') {
-      const results = await apiCall('search_semantic', { query: q, limit: 20, offset: nextOffset.value })
+      const results = await apiCall('search_semantic', { query: q, limit: 15, offset: nextOffset.value })
       const rawResults = (results?.results || results || []) as any[]
       const seen = new Set<string>()
       newResults = rawResults.filter(r => {
         const key = `${r.file_uuid}:${r.start_frame || 0}`
-        if (seen.has(key)) return false
+        const globalKey = `${r.file_uuid}:${r.start_frame || 0}:${r.source_type || 'unknown'}`
+        if (seen.has(key) || existingIds.has(globalKey)) return false
+        seen.add(key)
+        return true
+      }).map(r => ({ ...r, search_query: q })).slice(0, 10)
+    } else if (currentMode === 'agent') {
+      // Agent mode: fallback to semantic search for more results
+      const results = await apiCall('search_semantic', { query: q, limit: 15, offset: nextOffset.value })
+      const rawResults = (results?.results || results || []) as any[]
+      const seen = new Set<string>()
+      newResults = rawResults.filter(r => {
+        const key = `${r.file_uuid}:${r.start_frame || 0}`
+        const globalKey = `${r.file_uuid}:${r.start_frame || 0}:${r.source_type || 'unknown'}`
+        if (seen.has(key) || existingIds.has(globalKey)) return false
         seen.add(key)
         return true
       }).map(r => ({ ...r, search_query: q })).slice(0, 10)