Under Madam Speaker, Conflict Gives Way to Collaboration
Christine C Quinn has changed political environment of New York City Council in her first year as speaker; has emerged as influential partner of Mayor Michael R Bloomberg, changing high-stakes conflict between them to focus on effectiveness and collaboration; privately, some council members say Quinn has acquiesced too often, with Council overriding mayoral votes only twice in 2006, down from 15 in 2005; photos (M)