A surprising rise in the unemployment rate last month has rattled financial markets and set off new worries about the threat of a recession — but it could also prove to be a false alarm. Friday’s jobs report also showed hiring slowed last month. It coincides with other signs the economy is cooling amid high prices and elevated interest rates. The U.S. economy used to flash reliable signals when it was in or near a recession. But those red lights have gone haywire since the COVID-19 pandemic struck and upended normal business activity. Over the past two or three years, they’ve signaled downturns that never arrived as the economy just kept rolling along.