pi0_fast: fix off-by-one in next-token positions; add regression test#707

aryanrahar wants to merge 2 commits intoPhysical-Intelligence:mainPhysical-Intelligence/openpi:mainfrom

aryanrahar:fix/pi0fast-next-position-off-by-onearyanrahar/openpi:fix/pi0fast-next-position-off-by-oneCopy head branch name to clipboard