US regulators for the first time approved exchange-traded funds that invest directly in Bitcoin, a move heralded as a landmark event for the roughly $1.7 trillion digital-asset sector that will broaden access to the largest cryptocurrency on Wall Street and beyond.The Securities and Exchange Commission, whose three-part mandate includes investor protection, authorized funds from industry heavyweights BlackRock, Invesco and Fidelity to smaller competitors including Valkyrie to begin trading Thurs...