(Reuters) -Britain’s Superdry on Thursday signalled a strong start to the second half as online jacket sales hit a record high amid the Black Friday shopping spree and a recent spell of colder weather, sending its shares about 17% higher. The fashion retailer also reported first-half revenue growth of 3.6%, but struck a cautious note on outlook as the sector steers through rising expenses and a worsening cost-of-living crisis in the UK. “We are under no illusions that consumer confidence is fragile and that the picture is unlikely to change quickly,” said Superdry Chief Executive Officer Julia…