SAN SEBASTIAN — “Boy or girl?” jokes Adi (Adrian Schiop), poking the vast dome of a belly of boyfriend Alberto (Pavel Vasile-Digudai), who lies on his sofa, on which he takes up frequent residence, in the mid-stretch of “Soldiers. A Story from Ferentari.” Even in physical terms, the love story of Adi, a wiry thin-rim-glassed...