BEIRUT — After five years of bloodshed — after a quarter of a million deaths, and the flight of millions of refugees — Syria has arrived at a critical juncture: A diplomatic framework is in place to end the carnage, a two-week-old partial cease-fire is holding, and peace talks are set to resume in coming days. “The indicators from a distance are all good,” said Bassam Barabandi, a Washington-based former Syrian diplomat who now serves as a political adviser to the Syrian opposition.