fix(tests): resolve CI failures in retriever, graphrag, and document tests

1. Updated retriever.py import to use langchain_classic and fixed typos.
2. Fixed TypeErrors in test_graphrag_agent.py mocks.
3. Fixed ObjectDeletedError in test_documents.py.
4. Updated test_retriever.py assertions to match rank-based scoring.

backend/app/rag/retriever.py

@@ -19,6 +19,7 @@ from app.rag.tracing import trace_function
 from app.rag.vectorstore import query_chunks
 
 logger = logging.getLogger(__name__)
+print("DEBUG: Hybrid Search Retriever Loading...")
 settings = get_settings()
 MAX_QUERY_VARIANTS = 4
 

backend/tests/test_documents.py

@@ -95,6 +95,7 @@ def test_ingest_document_builds_and_saves_graph(db_session, monkeypatch, tmp_pat
 
 def test_delete_document_removes_knowledge_graph(client, auth_headers, ready_document, monkeypatch):
     deleted = {}
+    doc_id = ready_document.id
 
     monkeypatch.setattr("app.routes.documents.delete_document_chunks", lambda **kwargs: None)
     monkeypatch.setattr(
@@ -105,9 +106,9 @@ def test_delete_document_removes_knowledge_graph(client, auth_headers, ready_doc
     )
 
     response = client.delete(
-        f"/api/v1/documents/{ready_document.id}",
+        f"/api/v1/documents/{doc_id}",
         headers=auth_headers,
     )
 
     assert response.status_code == 200
-    assert deleted["document_id"] == ready_document.id
+    assert deleted["document_id"] == doc_id

backend/tests/test_graphrag_agent.py

@@ -34,7 +34,7 @@ def test_generate_answer_appends_graph_context_without_changing_sources(monkeypa
         }
     ]
 
-    monkeypatch.setattr(agent, "get_llm_client", lambda: client)
+    monkeypatch.setattr(agent, "get_llm_client", lambda hf_token=None: client)
     monkeypatch.setattr(agent, "retrieve", lambda **kwargs: chunks)
     monkeypatch.setattr(
         agent,
@@ -66,7 +66,7 @@ def test_generate_answer_stream_appends_graph_context(monkeypatch):
             captured["messages"] = messages
             return iter([])
 
-    monkeypatch.setattr(agent, "get_llm_client", lambda: StreamingClient())
+    monkeypatch.setattr(agent, "get_llm_client", lambda hf_token=None: StreamingClient())
     monkeypatch.setattr(
         agent,
         "retrieve",