The Nineteenth Biennale of Sydney may be remembered more for a boycott by participating artists than for the curatorial vision of artistic director Juliana Engberg, who subtitled the show “You Imagine What You Desire.” It is the blackest irony that the curator’s vision of art “imagining a world beyond the prosaic grounded life” should be ambushed by the festering political controversy surrounding Australia’s treatment of asylum seekers. The target of the artists’ protest was the Biennale’s sponsorship by Transfield Holdings, a shareholder in Transfield Services, which runs Australia’s offshore