LIBYA’S warring factions have signed a permanent ceasefire agreement, but any lasting end to years of chaos and bloodshed will require wider agreement among myriad armed groups and the outside powers that support them. Acting United Nations envoy Stephanie Williams said the ceasefire would start immediately and all foreign fighters must quit Libya within three months. Forces would withdraw from front lines and a new joint police force would secure those areas. As a first commercial passenger flight in more than a year crossed front lines from Tripoli to the eastern city of Benghazi on Friday, Williams noted Libya's "fraught"…