Photo: Daniel Shirey/MLB Photos/Getty Images Not long after he bought the Mets for $2.4 billion, the hedge-fund baron Steven A. Cohen had a deal in mind that was several times more lucrative. He wanted to build a massive casino and resort next door to the Mets’ home in Queens, Citi Field. If it worked, it would be one of the city’s largest real-estate development projects in decades. But while the deal was potentially more lucrative, it was also politically thorny. The competition to win one of