test(cqrs): 补充注册服务程序集去重测试

- 新增 DefaultCqrsRegistrationService 的独立测试文件，覆盖同次调用内的重复程序集键去重行为

- 验证跨两次调用重复程序集键时会跳过注册并写入 debug 日志

GFramework.Cqrs.Tests/Cqrs/CqrsRegistrationServiceTests.cs

@@ -0,0 +1,96 @@
+using GFramework.Core.Abstractions.Logging;
+using GFramework.Cqrs.Abstractions.Cqrs;
+using GFramework.Cqrs.Tests.Logging;
+
+namespace GFramework.Cqrs.Tests.Cqrs;
+
+/// <summary>
+///     验证 CQRS 程序集注册协调器在程序集键去重层面的可观察行为。
+/// </summary>
+[TestFixture]
+internal sealed class CqrsRegistrationServiceTests
+{
+    /// <summary>
+    ///     验证同一次调用内出现重复程序集键时，底层注册器只会接收到一次注册请求。
+    /// </summary>
+    [Test]
+    public void RegisterHandlers_Should_Register_Duplicate_Assembly_Key_Only_Once_Per_Call()
+    {
+        var logger = new TestLogger("DefaultCqrsRegistrationService", LogLevel.Debug);
+        var registrar = new Mock<ICqrsHandlerRegistrar>(MockBehavior.Strict);
+        var duplicateAssemblyA = CreateAssembly("GFramework.Cqrs.Tests.DuplicateAssembly, Version=1.0.0.0");
+        var duplicateAssemblyB = CreateAssembly("GFramework.Cqrs.Tests.DuplicateAssembly, Version=1.0.0.0");
+        var expectedAssembly = duplicateAssemblyA.Object;
+        IEnumerable<Assembly>? registeredAssemblies = null;
+
+        registrar
+            .Setup(static currentRegistrar => currentRegistrar.RegisterHandlers(It.IsAny<IEnumerable<Assembly>>()))
+            .Callback<IEnumerable<Assembly>>(assemblies => registeredAssemblies = assemblies.ToArray());
+
+        var service = CqrsRuntimeFactory.CreateRegistrationService(registrar.Object, logger);
+
+        service.RegisterHandlers([duplicateAssemblyA.Object, duplicateAssemblyB.Object]);
+
+        registrar.Verify(
+            static currentRegistrar => currentRegistrar.RegisterHandlers(It.IsAny<IEnumerable<Assembly>>()),
+            Times.Once);
+        Assert.Multiple(() =>
+        {
+            Assert.That(registeredAssemblies, Is.Not.Null);
+            Assert.That(registeredAssemblies, Is.EqualTo([expectedAssembly]));
+            Assert.That(logger.Logs, Has.Count.EqualTo(0));
+        });
+    }
+
+    /// <summary>
+    ///     验证跨两次调用重复程序集键时，协调器会跳过重复注册并写入 debug 日志。
+    /// </summary>
+    [Test]
+    public void RegisterHandlers_Should_Skip_Already_Registered_Assembly_Key_Across_Calls_And_Log_Debug_Message()
+    {
+        var logger = new TestLogger("DefaultCqrsRegistrationService", LogLevel.Debug);
+        var registrar = new Mock<ICqrsHandlerRegistrar>(MockBehavior.Strict);
+        var firstAssembly = CreateAssembly("GFramework.Cqrs.Tests.RegisteredAssembly, Version=1.0.0.0");
+        var secondAssembly = CreateAssembly("GFramework.Cqrs.Tests.RegisteredAssembly, Version=1.0.0.0");
+        IEnumerable<Assembly>? registeredAssemblies = null;
+
+        registrar
+            .Setup(static currentRegistrar => currentRegistrar.RegisterHandlers(It.IsAny<IEnumerable<Assembly>>()))
+            .Callback<IEnumerable<Assembly>>(assemblies => registeredAssemblies = assemblies.ToArray());
+
+        var service = CqrsRuntimeFactory.CreateRegistrationService(registrar.Object, logger);
+
+        service.RegisterHandlers([firstAssembly.Object]);
+        service.RegisterHandlers([secondAssembly.Object]);
+
+        registrar.Verify(
+            static currentRegistrar => currentRegistrar.RegisterHandlers(It.IsAny<IEnumerable<Assembly>>()),
+            Times.Once);
+        Assert.Multiple(() =>
+        {
+            Assert.That(registeredAssemblies, Is.EqualTo([firstAssembly.Object]));
+            Assert.That(
+                logger.Logs.Where(static log => log.Level == LogLevel.Debug).Select(static log => log.Message),
+                Is.EqualTo(
+                [
+                    "Skipping CQRS handler registration for assembly " +
+                    "GFramework.Cqrs.Tests.RegisteredAssembly, Version=1.0.0.0 because it was already registered."
+                ]));
+        });
+    }
+
+    /// <summary>
+    ///     创建一个带稳定程序集键的程序集 mock，用于模拟不同 <see cref="Assembly" /> 实例表示同一程序集的场景。
+    /// </summary>
+    /// <param name="assemblyFullName">要返回的程序集完整名称。</param>
+    /// <returns>配置好完整名称的程序集 mock。</returns>
+    private static Mock<Assembly> CreateAssembly(string assemblyFullName)
+    {
+        var assembly = new Mock<Assembly>();
+        assembly
+            .SetupGet(static currentAssembly => currentAssembly.FullName)
+            .Returns(assemblyFullName);
+
+        return assembly;
+    }
+}