A.I. may be advancing at breakneck speed, but Bill Gates worries its most powerful tools are reaching the wealthiest people and countries first. To help counter that, the 70-year-old Microsoft co-founder is committing at least $1 billion through his private foundation, trying to push the technology into the clinics, classrooms and farms that Silicon Valley might otherwise overlook. Backed by a trust that held a $92 billion endowment as of June, …