Eradicating homelessness would involve tacking systemic racism, reconstructing the nation's mental health, family support and substance abuse systems, raising wages, expanding the federal housing voucher program and building millions more subsidized homes.    Housing the homeless used to be something everybody agreed on.  That shift is partly fueled by violence like the killing this year of Christina Yuna Lee-in her apartment in Manhattan's Chinatown-and of Michelle Alyssa Go, who was shoved from a Times Square subway platform into an oncoming train. In each case, the police arrested a homeless man with a history of mental illness.   There's something new in America-an intolerance, a cultural shift.    During the last decade, Houston, the nations fourth most populous city, has moved more than 25,000 homeless people directly into apartments and houses.    The overwhelming majority of them have remained housed after two years.  The number of people deemed homeless in the Houston region has been cut by 63% since 2011, according to the latest numbers from local officials.      Even judging by the more modest metrics registered in a 2020 federal report, Houston did twice as well as the rest of the country at reducing homelessness over the previous decade.  Ten years ago, homeless veterans, one of the categories that the federal government tracks, waited 720 days and had to navigate 76 bureaucratic steps to get from the street into permanent housing with support from social service counselors. Today, a streamlined process means the wait for housing is 32 days.  Houston has gotten this far by teaming with county agencies and persuading scores of local services providers, corporations and charitable nonprofits-organizations that often bicker and compete with one another-to row in unison.  Together, they've gone all in on "housing first," a practice, supported by decades of research that moves the most vulnerable people straight from the streets into apartments, not into shelters, and without first requiring them to wean themselves off drugs or complete a 12-step program or find God or a job.        "We are not here to solve poverty. We aren't here to fix the affordable housing problem" is how Ms. Rausch puts it, adding, "Think of the homeless system in America as an emergency room for a triaged slice of poverty. What Houston has achieved is to get itself far enough along in addressing the challenge that we can hope to begin to think about the pipeline to homelessness."  One in every 14 Americans experiences homelessness at some point, a population that is disproportionately Black.