refactor: 重构战斗结构体以支持双打模式

logic/service/fight/node/skill.go

@@ -38,8 +38,11 @@ func (e *EffectNode) OnSkill() bool {
 }
 
 func (e *EffectNode) Skill_Can() bool {
-
-	return e.Input.CurPet[0].HP != 0
+	currentPet := e.Input.CurrentPet()
+	if currentPet == nil {
+		return false
+	}
+	return currentPet.HP != 0
 }
 
 func (e *EffectNode) GenSub(t input.Effect, Duration int) input.Effect {