fix: deduplicate knowledge content search results

ai_knowledge_base_v2/apps/backend/tests/test_knowledge_admin.py

@@ -325,8 +325,10 @@ def test_content_search_finds_current_sections_cards_and_chunks():
         response = content_search("静水流深", includeClosed=True, page=1, pageSize=10, db=db, current_admin=_admin())
 
         data = response["data"]
-        assert data["total"] == 3
-        assert {item["itemType"] for item in data["items"]} == {"section", "card", "chunk"}
+        assert data["total"] == 1
+        assert len(data["items"]) == 1
+        assert data["items"][0]["itemType"] == "section"
+        assert data["items"][0]["itemTypes"] == ["section", "card", "chunk"]
         assert data["items"][0]["sectionKey"] == "S0098"
         assert data["items"][0]["hasChunks"] is True
         assert data["items"][0]["canAgentUse"] is True