There’s some urgency to the task. These days, investing firms figure they’ll either master the digital world or become yet another of Silicon Valley’s victims. Each year, Fidelity gathers scores of technologists and executives to confront threats to the 71-year-old business, which manages $2.4 trillion and is one of the world’s biggest mutual fund companies and retirement plan administrators. Like generals and soldiers in a war game, they sketch out what they would do in all kinds of scenarios, such as a market crash or a merger that created a super rival. Just as ominous, perhaps, they ask: What if Amazon distributed financial products or offered its own financial advice? What if Google bought its own money manager?