test(backend): parallelize isolated fixtures [CI] [SKIP TESTS]

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

@@ -132,8 +132,7 @@ public sealed class StaticSiteTests
 }
 
 /// <summary>HTTP 层：后端自己的路径不会被前端的回退吞掉；响应头对。</summary>
-[Collection("probe-e2e")]
-public sealed class StaticSiteHttpTests
+public sealed class StaticSiteHttpTests : IClassFixture<BackendFixture>
 {
     private readonly BackendFixture _backend;