NEW YORK — Tom Fontana’s fiefdom fits neatly in a red-brick, four-story, 19th-century West Village townhouse — its colossal, multistory windows befitting the library it was and still, in part, remains. Fontana bought and refurbished the building in 1997 with the relative fortune he made in an earlier golden age of TV — from his first writing break on “St. Elsewhere,” the ’80s NBC drama about a teaching hospital, then onward as writer-producer for NBC’s “Homicide: Life on the Street” in the ’90s, then as creator of “Oz,” the admired HBO prison drama that ended in 2003.