CHICAGO — Lori Lightfoot was sworn in as Chicago mayor Thursday, becoming the first black woman and the first openly gay person to hold the office in the city’s history.During her approximately half-hour speech, Lightfoot drew from Chicago poet Gwendolyn Brooks and called for citywide unity in addressing public safety, education, financial stability and “integrity” — a reference to Chicago’s infamous corruption.“For years, they’ve said Chicago ain’t ready for reform.