chat: only scrolltobottom if first backlog grab
chat: only scrolltobottom if first backlog grab

jfranklin9000/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,jfranklin9000/urbit