Flatbread: 1 envelope active dry yeast 2 tablespoons sugar 2 cups bread flour, divided 3/4 cup warm water, divided 2 teaspoons chopped rosemary 1/2 teaspoon fine salt 1/4 teaspoon freshly ground pepper Topping: 1/2 lb. red California grapes (1-1/2 cups) Coarse sea salt 3 ounces blue cheese, crumbled (1/2 cup) 1 tablespoon honey 1 tablespoon…