SITUATION EXPLAINED: AMD is buying World Labs for $8.2 billion, and Fei-Fei Li becomes its chief scientist. • All stock, closing by the end of the year. Li reports directly to Lisa Su • AMD was already an investor in World Labs' $1 billion round in February. So was Nvidia • @LisaSu : "The more you understand end-to-end, the better system you're going to build." World Labs' research should show AMD how workloads are evolving and shape its hardware roadmap • Two products. Marble generates…