feat: add query observability and collation safeguards

docs/API_INTEGRATION.md

@@ -267,6 +267,10 @@ GET  /api/knowledge/quality/assets/{assetId}/conflicts
 GET  /api/knowledge/quality/index-health
 GET  /api/knowledge/quality/metrics
 GET  /api/knowledge/quality/alerts?includeResolved=false&limit=100
+GET  /api/knowledge/quality/query-traces?status=&domain=&limit=50
+GET  /api/knowledge/quality/query-traces/{requestId}
+
+`query-traces` 仅返回租户内的结果摘要、候选通道/排序和证据使用状态，不返回原始问题、答案或附件正文；摘要字段由 `aihr_20260804_query_result_observability_mysql8.sql` 增量补齐。
 GET  /api/knowledge/quality/glossary?status=ACTIVE&limit=100
 POST /api/knowledge/quality/glossary
 POST /api/knowledge/quality/glossary/{id}/approve