Billionaire Mukesh Ambani takes the podium today for Reliance Industries Ltd.’s 49th annual general meeting (AGM) at 2 pm, and shareholders want one answer above all else: a date for the Jio IPO, which could become the mother of all public issues in the country.Reliance shares are down 17% from their 52-week high as turmoil in the Gulf weighs on the conglomerate’s core refining business. The stock has fallen 16% so far this year, making it one of the worst performers on the benchmark BSE Sensex.The slide has wiped $19 billion off Ambani’s fortune, knocking him off the top spot…