No curtain separates audience from stage in “Bluebirds,” a new play by Joe Brondo that opened last weekend at Guild Hall and will run through Sunday. The audience enters the theater to the sound of music and a brightly lit set of well-worn living room furniture placed downstage. A digital clock says it’s 12:01. After a few minutes, a man bursts through the door and runs full speed off stage left. He is followed by a woman, who turns off the theater lights with a switch on the living room wall and cuts the music with a remote aimed at the audience. A toilet flushes offstage.