Nvidia is facing an unprecedented valuation test as a board inquiry into CEO Jensen Huang exposes the US chipmaker to a rare key-person risk, while investors also weigh the midterm elections’ potential impact on Washington’s chip controls and AI regulation. The company’s shares slumped 7.3 per cent as markets opened in the United States on Monday, following Huang’s bombshell confirmation over the weekend that he had been unfaithful to his wife and would cooperate with an investigation into his...