NEW YORK—Stephen Sondheim, the songwriter who reshaped American musical theater in the second half of the 20th century with his intelligent, intricately rhymed lyrics, his use of evocative melodies, and his willingness to tackle unusual subjects, has died. He was 91. Sondheim’s death was announced by Rick Miramontez, president of DKC/O&M. Sondheim’s Texas-based attorney, Rick Pappas, told The New York Times the composer died Friday at his home in Roxbury, Connecticut. Tributes quickly flooded social media as performers and writers alike saluted him. “We shall be singing your songs forever,” wrote Lea Salonga. Aaron Tveit wrote: “We are so lucky to have what you’ve given the world.” “The theater has lost one of its greatest geniuses and the world has lost one of its greatest and most original writers. Sadly, there is now a giant in the sky,” producer Cameron Mackintosh wrote in a tribute. Music supervisor, arranger, and orchestrator …