Condition-driven multi-stage quests on top of the foundation: Quest/QuestStage
data, QuestLog + QuestEngine (per-turn auto-advance with announcements),
START_QUEST effect, QuestView display via a console 'quests' command and a GUI
quest-box under the map. quests.yaml optional; World gains a 5-arg back-compat
constructor. Win/endings deferred to 3.3.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
