Mash chickpeas roughly in a bowl with a fork. Leave some whole pieces.
Mix in yogurt, mustard, lemon juice, celery, carrot, and pepper. Taste and adjust.
Lay out tortillas and add lettuce, leaving a border around the edges.
Divide filling between tortillas. Fold in the sides, roll firmly, and cut in half.
Storage: Refrigerate perishables promptly in shallow containers. Use refrigerated leftovers within 3–4 days or freeze earlier. Reheat cooked leftovers to 165°F; keep cold meals chilled during transport. Follow ingredient labels if they require a shorter storage time.