Priority-ordered condition-driven endings + an end-of-game summary (turns,
quests X/Y, rank). EndingEngine mirrors the quest engine; Game ends the loop
when an ending fires. endings.yaml optional; World gains 5/6/7-arg back-compat
constructors. Two reachable demo endings (victory, flee) with no new mechanics.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
