perf(tests): isolate network E2E and await QUIC cleanup

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

@@ -184,6 +184,7 @@ public sealed class HostStatusTests : IClassFixture<BackendFixture>
     }
 
     [Fact]
+    [Trait("Category", "Slow")]
     public async Task ARealProbeReportsItsHostStatus_LikeAnAgent_NeverCarriesModelsOrAddresses_AndDisappearsWhenRevoked()
     {
         await _backend.SiteMustBePublicAsync();