修复(AI客服): 退款操作统一转人工处理

隐藏并拦截退款类业务动作，兼容旧确认流程，确保所有客户类型的退款请求进入人工支持，并补充回归测试。

internal/ai/application/runtime/customer_after_sales_policy_test.go

@@ -178,3 +178,22 @@ func TestKnowledgeFallbackAllowsOrdinaryAutonomousAnswers(t *testing.T) {
 		}
 	}
 }
+
+func TestRefundPolicyAppliesToEveryCustomerSegment(t *testing.T) {
+	for _, customerType := range []string{"card", "device", "mall_user", ""} {
+		t.Run(customerType, func(t *testing.T) {
+			engine := NewAgentLoopEngine()
+			engine.retrieve = nil
+			engine.history = nil
+			turn := engine.prepareTurn(context.Background(), RunInput{
+				Conversation: models.Conversation{CustomerType: customerType},
+				UserMessage:  models.Message{Content: "我要退款，我已经确认了"},
+			}, nil)
+			for _, want := range []string{"退款必须由人工客服处理", "即使客户明确授权或确认也不允许", "不得进入退款确认流程", "人工客服", "客户仅查询退款政策或进度时", "Refund requests are human-only", "available permitted write operation"} {
+				if !strings.Contains(turn.SystemPrompt, want) {
+					t.Fatalf("refund policy missing %q", want)
+				}
+			}
+		})
+	}
+}