feat(engine): 实现阵营博弈机制

- FactionData 新增 threshold 和 skill 字段
- 修改能量累积逻辑：power 跨 tick 累积
- 阈值改为 10，达到后触发阵营技能
- festival 提升情绪，panic 降低情绪

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

engine-python/app/state.py

@@ -31,8 +31,8 @@ def get_default_state() -> WorldState:
         events=[],
         global_meter=GlobalMeter(value=0, threshold=100, cooldown=0),
         factions=Factions(
-            optimists=FactionData(power=0, members=[]),
-            fearful=FactionData(power=0, members=[])
+            optimists=FactionData(power=0, threshold=10, skill="festival", members=[]),
+            fearful=FactionData(power=0, threshold=10, skill="panic", members=[])
         ),
         story_arcs=get_default_story_arcs(),
     )