change last 4 history(2 round) to last 5 round

src/app.py

@@ -288,8 +288,8 @@ if user_input := st.chat_input("Ask me questions about the CANMAT depression gui
     st.session_state.last_top_p_used = top_p
     st.session_state.last_max_length_used = max_length
 
-    # ===== latest 4 histories =====
-    history = st.session_state.messages[:-1][-4:]
+    # ===== latest 10 histories(5 round) =====
+    history = st.session_state.messages[:-1][-10:]
 
     placeholder = st.chat_message("assistant").empty()
     collected = ""
@@ -316,7 +316,6 @@ if user_input := st.chat_input("Ask me questions about the CANMAT depression gui
                 collected += chunk
                 placeholder.markdown(collected)
         finally:
-            # 恢复原始的 client
             Rag.llm_client = original_client
         
         t1 = time.perf_counter()