In a small bowl, whisk the peanut butter with the soy sauce, lime zest, lime juice, brown sugar, chile garlic sauce, ginger, garlic, and warm water until smooth. Add more water, if needed, until the sauce is a pourable consistency. Adjust to taste with more soy sauce, lime juice, and chile garlic sauce.
Warm the JSF Beef Fajitas according to package instructions.
In a large pot of salted boiling water, cook the pasta according to package instructions. Drain well. Toss the spaghetti with the peanut sauce and season with salt.
Meanwhile, using a vegetable peeler or a mandolin, slice the cucumbers lengthwise into long thin ribbons.
Divide the noodles between four shallow bowls. Top with the steak and shaved cucumbers. Season the cucumbers with a little salt. Garnish the bowls with scallions, cilantro, and chopped peanuts. Serve right away, passing lime wedges at the table.