Gene Maddaus Senior Media WriterThe gaffer on “Rust” felt a whoosh of air and heard the loudest shot he had ever heard on set, and then watched helplessly as his friend Halyna Hutchins faded away in his arms, according to a lawsuit filed on Tuesday.Serge Svetnoy provided a detailed, first-hand account of the Oct. 21 shooting in a negligence suit against several defendants, including “Rust” star Alec Baldwin, the film’s producers, the armorer and first assistant director.