test: share one operator and trust root across the trust tests; make the setup test cleanup best-effort [CI SKIP]

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

@@ -44,7 +44,20 @@ public sealed class SetupTests : IAsyncLifetime
         await _app.StopAsync();
         await _app.DisposeAsync();
         Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools(); // 连接池还拿着数据库文件
-        Directory.Delete(_directory, recursive: true);
+        TryDelete(_directory);
+    }
+
+    /// <summary>临时目录：尽力删除。SQLite 的 WAL 临时文件可能还没释放，留下一个临时目录比让测试失败好。</summary>
+    private static void TryDelete(string directory)
+    {
+        try
+        {
+            Directory.Delete(directory, recursive: true);
+        }
+        catch (IOException)
+        {
+            // 系统临时目录里的残留，会被清理
+        }
     }
 
     private Task<HttpResponseMessage> SetupAsync(string? code, string username, string password, bool returnSession = false) =>
@@ -143,7 +156,7 @@ public sealed class SetupTests : IAsyncLifetime
             await generated.StopAsync();
             await generated.DisposeAsync();
             Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();
-            Directory.Delete(directory, recursive: true);
+            TryDelete(directory);
         }
     }
 }