New York City’s bonds have suddenly become a hot topic on Wall Street — and you can thank socialist Mayor Zohran Mamdani for this certifiably bizarre development. This past week, the Big Apple went to investors to sell billions of dollars in municipal debt. With Mamdani doing his best imitation of Fidel Castro, the city sold $2.3 billion — $300 million less than it had targeted. Mind you, I’ve been covering NYC bond deals for decades. For the most part, they’ve been what you might call boring —