LAS VEGAS — Across their 43 seasons, the Washington Capitals have dabbled in hapless hockey and exquisite hockey, boring hockey and effective hockey, but never had they played winning hockey through four playoff rounds, all the way to a grueling, glorious end. It took a team hardened by those postseason failures but liberated from high expectations to complete a run as dazzling as it was cathartic, capping it on Thursday night by dispatching the upstart Vegas Golden Knights, 4-3, to win the first Stanley Cup in franchise history. It was the Capitals’ fourth consecutive victory in the finals after a disorienting 6-4 loss in the opener that made little sense in the context of how they played immediately before and afterward. After twice shutting out the offensive powerhouse Tampa Bay Lightning to advance to its first Cup finals since 1998, Washington outscored the Golden Knights across these last four games by 16-8. Lars Eller scored the winning goal with 7 mi...