feat(engine): add faction power system with event triggers

- Add FactionData model with power and members fields
- Add FactionEventResult model for faction event responses
- Add faction field to AgentState
- Implement faction classification based on emotion
- Add faction event triggers (festival/panic) when power >= 5
- Update StepResponse to include triggered_faction_event
- Add tests for new faction system

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

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

engine-python/app/main.py

@@ -2,6 +2,7 @@ from fastapi import FastAPI
 from .models import StepRequest, StepResponse
 from .state import load_state, save_state
 from .engine import process_events, generate_actions, check_and_trigger_global_event
+from .factions import check_and_trigger_faction_event
 
 app = FastAPI(title="AI Town Engine", version="0.1.0")
 
@@ -18,6 +19,9 @@ def step(request: StepRequest) -> StepResponse:
     # 检查并触发世界级事件
     state, global_event_result = check_and_trigger_global_event(state)
 
+    # 检查并触发阵营事件
+    faction_event_result = check_and_trigger_faction_event(state)
+
     # 生成 agent 行动
     actions = generate_actions(state)
 
@@ -27,7 +31,8 @@ def step(request: StepRequest) -> StepResponse:
     return StepResponse(
         world_state=state,
         actions=actions,
-        global_event=global_event_result
+        global_event=global_event_result,
+        triggered_faction_event=faction_event_result
     )