Add potatoes to a small saucepan and cover with salted water; bring to a boil over high heat. Reduce heat and simmer 10 minutes or until fork-tender. Drain and transfer potatoes to a bowl; mash until mostly smooth with a few small chunks remaining.

In the same saucepan, heat oil over medium heat. Add onion and cook, stirring occasionally, until tender, about 3 to 4 minutes. Stir in ginger and garlic; cook until fragrant, about 30 seconds. Add garam masala, cumin, salt, and cayenne pepper (if using); cook about 30 seconds more. Stir in mashed potatoes and peas; cook until warmed through. Remove from heat; stir in cilantro.

Arrange wonton wrappers on a clean work surface; spoon filling into centers of each wrapper. Lightly wet borders of wrappers with water. Fold two corners together to form triangles. Press edges to seal. Coat both sides of samosas with cooking spray.

Preheat air fryer to 350 degrees F (175 degrees C). Coat air fryer basket with cooking spray. Working in batches if needed, arrange samosas in an even layer in the basket. Cook, turning once halfway through, until samosas are golden brown and crispy, about 8 minutes.

Meanwhile, combine yogurt, cilantro, lime zest, lime juice, garlic, and black pepper in a small food processor; process until well combined. Chill, covered, up to 5 days.