ci: gate on the fast tests (about 20s); slow end-to-end tests run in parallel with the image build [CI]

backend/tests/MoShiro.Backend.Tests/Ipv6Tests.cs

@@ -9,7 +9,9 @@ using MoShiro.TestSupport;
 namespace MoShiro.Backend.Tests;
 
 /// <summary>真实双栈回环：同一身份的两种会话、原始块、查询与测试结果必须各自独立。</summary>
+// 慢的端到端测试（真实时间的阶梯、要等测量块出来）：CI 里单独一批跑（Category=Slow），不拦着出镜像，见 ci/verify-backend.sh
 [Collection("probe-e2e")]
+[Trait("Category", "Slow")]
 public sealed class Ipv6Tests
 {
     private readonly BackendFixture _backend;