He is one of her supermodels. He sits still, with his paws together. He preens his black snout into the air. His deep brown eyes stare into her camera. But Choco Taco, a black Collie mix, will stay at the Bond Between, a Minnetonka animal rescue, for longer than his spotted siblings, Executive Director Rachel Mairose suspects. Black dogs like Choco Taco are the trickiest to photograph, and …