By Gerry Shih and Lorenzo Tugnoli in The Washington Post, July 20 at 9:00 a.m.CHAPA DARA, Afghanistan — Sayed Wali Sajid spent years fighting American soldiers in the barren hills and fertile fields of the Pech River Valley, one of the deadliest theaters of the 20-year insurgency. But nothing confounded the Taliban commander, he said, like the new wave of foreigners who began showing up, one after another, in late 2021. Once, Sajid spotted a…