The idea there is gradual disengagement. US troops reduce their presence, spending generous amounts of money to build up the Afghans as we leave. Negotiate as good a settlement as we can with the Taliban. Don't see much danger of al Qaeda taking advantage of the US withdrawal as the Taliban blame al Qaeda for their loss of office in the first place.
Can't guarantee that things'll turn out fine. As the piece puts it, such a strategy will be a step off into darkness. But to stay and escalate pretty much guarantees a repeat of the Soviet experience.