Coupang Inc. slid in late trading on Tuesday after reporting retail net sales that fell short of Wall Street’s expectations.Net sales totaled $6.14 billion, up from a year earlier but below analysts’ estimates of $6.24 billion. Operating income totaled $109 million, also slipping below projections. Net income fell in the quarter, reflecting losses at Farfetch, the online luxury company Coupang acquired in January....