If fears about “the bomb” permeated life in the mid-20th century, the video game “Fallout” takes that premise to its worst conclusion. In a post-nuclear wasteland, some survivors have been recreating their 1950s-era idyll underground in elaborate bomb shelters called vaults. Those less lucky have been eking out a life on the surface, where it is dusty and brutal, and nasty oddities abound in the…