Pour 1 1/2 cups boiling water mixed with 1/8 teaspoon of the salt over the couscous in a small bowl. Cover well and set aside.
To make the pesto: Combine the garlic, basil, olive oil, remaining 1/8 teaspoon salt, and pepper in a blender. Blend well until smooth. Stir in the cheese.
Toast the walnuts in a small heavy dry skillet over medium heat, stirring constantly, until aromatic, watching closely to prevent burning, about 3 to 5 minutes. Set aside.
To assemble: Heat the tortillas, one at a time, directly on a gas flame, on a grill, or in a hot skillet, turning frequently, until hot and pliable, about 5 to 15 seconds each. Or heat, stacked between 2 damp paper towels, in the microwave for about 10 seconds per tortilla. Distribute 2 tablespoons pesto, 1/2 scant cup couscous, 3/4 to 1 cup chicken, and a quarter of the walnuts, sun-dried tomatoes, and peppers evenly over tortilla, leaving a 1-inch border. Roll up into a wrap. Complete the wraps with the remaining ingredients. Or if you prefer, prepare all at once, assembly-line style. Cut in half on the bias.