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/models.py

@@ -44,11 +44,22 @@ class Stance(BaseModel):
     fear: float = Field(default=0.5, ge=0.0, le=1.0)
 
 
+class FactionData(BaseModel):
+    """单个派系的数据"""
+    power: int = 0
+    members: List[str] = Field(default_factory=list)
+
+
 class Factions(BaseModel):
-    """派系分布"""
-    optimists: int = 0
-    fearful: int = 0
-    neutral: int = 0
+    """派系分布（带 power 和 members）"""
+    optimists: FactionData = Field(default_factory=FactionData)
+    fearful: FactionData = Field(default_factory=FactionData)
+
+
+class FactionEventResult(BaseModel):
+    """阵营事件触发结果"""
+    type: Optional[str] = None  # "festival" | "panic" | None
+    source_faction: Optional[str] = None  # "optimists" | "fearful"
 
 
 class AgentState(BaseModel):
@@ -60,6 +71,8 @@ class AgentState(BaseModel):
     commented_effects: List[str] = Field(default_factory=list)
     # 角色立场
     stance: Stance = Field(default_factory=Stance)
+    # 所属阵营
+    faction: str = "neutral"  # "optimists" | "fearful" | "neutral"
 
 
 class WorldState(BaseModel):
@@ -106,3 +119,4 @@ class StepResponse(BaseModel):
     world_state: WorldState
     actions: List[Action]
     global_event: GlobalEventResult = Field(default_factory=GlobalEventResult)
+    triggered_faction_event: FactionEventResult = Field(default_factory=FactionEventResult)