v2 message format and upgrade to ai sdk v5 (#743)

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Liang-Shih Lin <liangshihlin@proton.me>
Co-authored-by: Dominik Engelhardt <dominikengelhardt@ymail.com>
Co-authored-by: Jay V <air@live.ca>
Co-authored-by: adamdottv <2363879+adamdottv@users.noreply.github.com>