New York City is now a little more completely Democratic. The party's tent grew yesterday with the defection of Councilman Peter Koo of Flushing, as reported in the Daily News. Koo won't magically transform into a left-winger, but as a liberal Republican he was at odds with his former party on immigration and social issues and a general aloofness to Asian-American issues. Beside that, as the Daily News has it, Koo learned quickly the limits of being in the minority party of the City Council. Koo, a millionaire pharmacist, can now rise with the tide that never fails to lift the Democratic boats in New York City.