feat: integrate new merge_groups API from Core Team

Replace merge_trace implementation with merge_groups API

Changes:
1. src/api/index.ts:
   - Add merge_groups API definition
   - POST /api/v1/file/:file_uuid/groups/merge
   - Parameters: file_uuid, source_groups[], target_group_name

2. src/views/PeopleView.vue:
   - Rewrite executeMerge() function
   - Use group names instead of trace IDs
   - Single API call for all groups
   - Remove trace-level loop

3. src/views/PeopleView.vue:
   - Delete updateClusterAfterMerge() function
   - No longer needed with new API

Benefits:
- ✅ Atomic operation (single API call)
- ✅ Correct merge behavior (groups, not traces)
- ✅ Better performance (1 call vs N calls)
- ✅ Data consistency guaranteed

API behavior:
- Merge N groups into 1 target group
- All traces from source groups merged to target
- Source groups deleted after merge
- Returns traces_merged count

Core API: Implemented by Core Team (2026-07-25)
Status: Ready for testing

src/api/index.ts

@@ -359,6 +359,17 @@ case 'search_keyword': {
     case 'merge_trace': {
       return { url: `/api/v1/file/${a.file_uuid}/trace/${a.source_id}/merge/${a.target_id}`, method: 'POST' }
     }
+    case 'merge_groups': {
+      return {
+        url: `/api/v1/file/${a.fileUuid}/groups/merge`,
+        method: 'POST',
+        body: {
+          file_uuid: a.fileUuid,
+          source_groups: a.sourceGroups,
+          target_group_name: a.targetGroupName
+        }
+      }
+    }
     case 'bind_face': {
       const bindBody: any = { file_uuid: a.fileUuid }
       if (a.faceId) bindBody.face_id = a.faceId

src/views/PeopleView.vue

@@ -1725,18 +1725,10 @@ async function executeMerge(targetGroupId: string) {
   console.log('[executeMerge] targetGroup:', targetGroup)
   if (!targetGroup) return
   
-  const targetTraceId = targetGroup.trace_ids?.[0]
-  console.log('[executeMerge] targetTraceId:', targetTraceId, typeof targetTraceId)
-  if (!targetTraceId) {
-    alert('Target group has no traces')
-    return
-  }
-  
-  const targetTrace = clusterTracesMap.value[String(targetTraceId)]
-  console.log('[executeMerge] targetTrace:', targetTrace)
-  const targetFileUuid = targetTrace?.file_uuid
-  if (!targetFileUuid) {
-    alert('Target trace has no file_uuid')
+  const targetGroupName = targetGroup.name
+  console.log('[executeMerge] targetGroupName:', targetGroupName)
+  if (!targetGroupName) {
+    alert('Target group has no name')
     return
   }
   
@@ -1745,71 +1737,48 @@ async function executeMerge(targetGroupId: string) {
   const sourceGroups = clusterAsPending.value.filter((c: any) => sourceGroupIds.includes(c.identity_uuid))
   console.log('[executeMerge] sourceGroups:', sourceGroups.length)
   
-  let totalTraces = 0
-  let validTraces = 0
-  for (const g of sourceGroups) {
-    for (const tid of g.trace_ids || []) {
-      totalTraces++
-      const t = clusterTracesMap.value[String(tid)]
-      if (t?.file_uuid) validTraces++
-    }
-  }
+  const sourceGroupNames = sourceGroups.map(g => g.name).filter(Boolean)
+  console.log('[executeMerge] sourceGroupNames:', sourceGroupNames)
   
-  console.log('[executeMerge] totalTraces:', totalTraces, 'validTraces:', validTraces)
-  
-  if (validTraces === 0) {
-    alert('No valid traces to merge (all missing file_uuid)')
+  if (sourceGroupNames.length === 0) {
+    alert('No valid source groups to merge')
     return
   }
   
-  if (!confirm(`Merge ${validTraces}/${totalTraces} trace(s) from ${sourceGroups.length} group(s)?`)) return
+  if (!confirm(`Merge ${sourceGroupNames.length} group(s) into "${targetGroupName}"?`)) return
   
   operationLoading.value = true
-  operationMessage.value = `Merging ${validTraces} trace(s)...`
+  operationMessage.value = `Merging ${sourceGroupNames.length} group(s)...`
   
-  let successCount = 0
-  let failCount = 0
-  
-  for (const g of sourceGroups) {
-    for (const srcTraceId of g.trace_ids || []) {
-      const srcTrace = clusterTracesMap.value[String(srcTraceId)]
-      const srcFileUuid = srcTrace?.file_uuid
-      if (!srcFileUuid) {
-        console.warn('[merge] skipping trace without file_uuid:', srcTraceId)
-        failCount++
-        continue
-      }
-      if (srcFileUuid !== targetFileUuid) {
-        console.warn('[merge] skipping cross-file trace:', srcTraceId, srcFileUuid, '!=', targetFileUuid)
-        failCount++
-        continue
-      }
-      try {
-        console.log('[executeMerge] calling merge_trace:', {
-          file_uuid: srcFileUuid,
-          source_id: srcTraceId,
-          target_id: targetTraceId
-        })
-        await apiCall('merge_trace', { 
-          file_uuid: srcFileUuid, 
-          source_id: srcTraceId, 
-          target_id: targetTraceId 
-        })
-        successCount++
-      } catch (e) {
-        console.error('Merge trace failed:', srcTraceId, e)
-        failCount++
-      }
+  try {
+    console.log('[executeMerge] calling merge_groups API:', {
+      fileUuid: selectedFileUuid.value,
+      sourceGroups: sourceGroupNames,
+      targetGroupName: targetGroupName
+    })
+    
+    const result = await apiCall('merge_groups', {
+      fileUuid: selectedFileUuid.value,
+      sourceGroups: sourceGroupNames,
+      targetGroupName: targetGroupName
+    })
+    
+    console.log('[executeMerge] result:', result)
+    
+    if (result?.success) {
+      console.log('[executeMerge] success, traces_merged:', result.traces_merged)
+      await loadClusterResults()
+      clearSelection()
+    } else {
+      alert(`Merge failed: ${result?.error || 'Unknown error'}`)
     }
+  } catch (e) {
+    console.error('[executeMerge] error:', e)
+    alert(`Merge failed: ${e}`)
+  } finally {
+    operationLoading.value = false
+    operationMessage.value = ''
   }
-  
-  console.log('[executeMerge] completed:', successCount, 'success,', failCount, 'failed')
-  
-  operationLoading.value = false
-  operationMessage.value = ''
-  
-  clearSelection()
-  await loadClusterResults()
 }
 
 async function batchMoveFaces() {