A sickle to the back! Mayor Zohran Mamdani’s allies are publicly breaking with him over his handpicked police commissioner — and Hizzoner is livid that the socialist House candidate he went out on a limb to endorse is leading the charge. City Hall staffers have been openly whining about alleged ally Darializa Avila Chevalier — whom Mamdani endorsed just a few months ago during the primaries — after she led a crusade to slam NYPD Commissioner Jessica Tisch after ICE agents shot an illegal migrant in the Bronx. “They were pissed about what she did on social media and her...