In the distant Koprulu Sector of the Milky Way, Facebook’s Zerglings lingered in a restless swarm outside the enemy’s base. After the commander ill-advisedly opened the gate, the social network’s alien horde stormed in and slaughtered forces stationed inside, in a battle fought on the frontiers of artificial-intelligence research. The bloody incident was part of an annual competition of the videogame StarCraft for AI software bots that wrapped up Sunday.