McDonald’s saw a key sales metric jump in the third quarter as it doubled down on discount meals – but it fell short on earnings as it warned anxious Americans have cut back on dining out.US same-store sales increased 2.4% for the second straight quarter. That beat estimates of a 1.9% rise – though McDonald’s attributed this to a larger average check, implying diners are paying more for their meals despite the fast-food industry’s “value wars.”Overall same-store sales rose 3.6%, reversing a decline of 1.5% ...