A sharp sell-off has reset expectations for the country's largest used car retailer -- and the long-term story still looks intact.CarMax (KMX -1.61%), the leading omnichannel seller of used vehicles, was hit hard after its latest update. The stock fell more than 20% on Thursday following weaker-than-expected results and a cautious tone on demand. Additionally, the market's reaction may also reflect mounting concerns about credit trends inside CarMax Auto Finance and the durability of consumer demand as rate ...