feat: RAG Integration (#238)

* feat: add rag provider and retriever

* feat: retriever tool

* feat: add retriever tool to the researcher node

* feat: add rag http apis

* feat: new message input supports resource mentions

* feat: new message input component support resource mentions

* refactor: need_web_search to need_search

* chore: RAG integration docs

* chore: change example api host

* fix: user message color in dark mode

* fix: mentions style

* feat: add local_search_tool to researcher prompt

* chore: research prompt

* fix: ragflow page size and reporter with

* docs: ragflow integration and add acknowledgment projects

* chore: format

src/rag/builder.py

@@ -0,0 +1,11 @@
+from src.config.tools import SELECTED_RAG_PROVIDER, RAGProvider
+from src.rag.ragflow import RAGFlowProvider
+from src.rag.retriever import Retriever
+
+
+def build_retriever() -> Retriever | None:
+    if SELECTED_RAG_PROVIDER == RAGProvider.RAGFLOW.value:
+        return RAGFlowProvider()
+    elif SELECTED_RAG_PROVIDER:
+        raise ValueError(f"Unsupported RAG provider: {SELECTED_RAG_PROVIDER}")
+    return None