In 2017, San Francisco’s top officials announced an audacious goal: Cut the city’s chronic homelessness number in half over the next five years. A few months earlier, the city had received support to help reach that goal — $100 million in pledged private expenditures from a nonprofit aiming for the same five-year reduction, complementing the city’s more than $250 million annual homelessness budget. “This is going to be huge,” then-Mayor Ed Lee told The Chronicle at the time about the initiative by nonprofit Tipping Point. “I do believe we’ll be able to cut chronic homelessness in half with this help.”...