The first faint signs of the football and the silly seasons showed up simultaneously: there were airliners stacked in lazy holding patterns all over the East; trains on the Long Island Rail Road were mysteriously missing; subways and other services were erratic. And there was the Jets' Joe Namath handsomely reflecting this new national mood of...well, not exactly striking but moving a bit slower. Namath's much-operated knees were too sore to play the first two games, he said, so he suited up in his sideburns and stylish blazer to serve as a spotter. Then Joe got fitted for his new double-breasted Blackglama mink overcoat. Furrier Hy Rifkin, that man tugging at the hem, said it was a $5,000 number, although Joe did not pay that much because, after all, one look at Namath and sportsmen everywhere will want fashionable furs.