Feat: TOC retrieval (#10456)

### What problem does this PR solve?

#10436

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/db/services/dialog_service.py

@@ -466,6 +466,10 @@ def chat(dialog, messages, stream=True, **kwargs):
                     rerank_mdl=rerank_mdl,
                     rank_feature=label_question(" ".join(questions), kbs),
                 )
+                if prompt_config.get("toc_enhance"):
+                    cks = retriever.retrieval_by_toc(" ".join(questions), kbinfos["chunks"], tenant_ids, chat_mdl, dialog.top_n)
+                    if cks:
+                        kbinfos["chunks"] = cks
             if prompt_config.get("tavily_api_key"):
                 tav = Tavily(prompt_config["tavily_api_key"])
                 tav_res = tav.retrieve_chunks(" ".join(questions))