Sergey Brin is the third richest person alive, worth roughly $240 billion, and he just took direct command of Gemini. He retired in 2019. He owns around 6% of a $3.9 trillion company. He could spend the next 40 years on a yacht without ever checking a price tag. Instead he's been at the office three to four days a week, in the weeds, writing code. Demis Hassabis confirmed it himself this year, "Sergey has been in the weeds, programming." The last time Brin was this hands-on, Google was…