How long until the start of the 2028 Summer Olympics in Los Angeles? Casey Wasserman responds immediately — “1,487 days” — no need to think it over. “It’s on my phone,” he says. “And I look at it every morning.” As chairman of the private group in charge of staging the Games, Wasserman also knows there is much to do before then. He muses: “We can’t buy more time.” The clock is very much ticking for LA28, which will reach a critical juncture after the close of the Paris Games. Gone is the initial blush of being named host. Gone are the years of brainstorming over how to give the Olympics a dist…