The neighbors paid landscape architect Gregory Lombardi the ultimate compliment when they began walking by the custom-designed fence he installed around a very visible Cambridge house without doing a double take. By any standard, it is a remarkable fence. But it fits with its softly layered landscape so seamlessly that nobody points and stares. “Everyone began assuming the fence has always been here,” Lombardi says proudly of the Brattle Street residence, “and that’s the way design should be.”