pop the cost and rename reset

app.py

@@ -34,6 +34,7 @@ def undo():
     if len(st.session_state.messages) > 0:
         st.session_state.messages.pop()
         st.session_state.messages.pop()
+        st.session_state.cost.pop()
         st.rerun()
 
 def share():
@@ -55,7 +56,7 @@ with st.sidebar:
         if st.button("Undo"):
             undo()
     with cols[1]:
-        if st.button("Clear chat"):
+        if st.button("Restart"):
             st.session_state.messages = []
             clear_uploader()