test(cqrs): 添加 CQRS 处理器注册生成器测试

- 创建 MetadataReferenceTestBuilder 工具类用于构建内存元数据引用
- 实现 CreateFromSource 方法将源码编译为内存程序集并返回元数据引用
- 添加 GetRuntimeMetadataReferences 方法获取当前运行时可信平台程序集引用
- 创建 CqrsHandlerRegistryGeneratorTests 测试类验证 CQRS 处理器注册生成器功能
- 添加多种测试用例验证不同场景下的处理器注册行为
- 包含嵌套处理器、隐藏实现、数组类型参数、泛型类型定义等边界情况测试
- 实现混合直接注册和精确重建注册的测试验证
- 添加对外部基类保护类型处理器的支持测试
- 验证生成器优先处理隐藏处理器而不输出遗留回退标记的功能

GFramework.SourceGenerators.Tests/Core/MetadataReferenceTestBuilder.cs

@@ -1,6 +1,5 @@
 using System.Collections.Immutable;
 using System.IO;
-using Microsoft.CodeAnalysis.CSharp;
 
 namespace GFramework.SourceGenerators.Tests.Core;
 
@@ -9,6 +8,11 @@ namespace GFramework.SourceGenerators.Tests.Core;
 /// </summary>
 public static class MetadataReferenceTestBuilder
 {
+    // Reuse the runtime reference set across generator tests to avoid reparsing TRUSTED_PLATFORM_ASSEMBLIES
+    // for every in-memory compilation.
+    private static readonly Lazy<ImmutableArray<MetadataReference>> CachedRuntimeReferences =
+        new(CreateRuntimeMetadataReferences);
+
     /// <summary>
     ///     将给定源码编译为内存程序集，并返回可供测试编译消费的元数据引用。
     /// </summary>
@@ -22,7 +26,7 @@ public static class MetadataReferenceTestBuilder
         params MetadataReference[] additionalReferences)
     {
         var syntaxTree = CSharpSyntaxTree.ParseText(source);
-        var references = GetRuntimeMetadataReferences()
+        var references = CachedRuntimeReferences.Value
             .Concat(additionalReferences)
             .ToImmutableArray();
         var compilation = CSharpCompilation.Create(
@@ -53,6 +57,11 @@ public static class MetadataReferenceTestBuilder
     /// </summary>
     /// <returns>当前运行时可信平台程序集对应的元数据引用。</returns>
     public static ImmutableArray<MetadataReference> GetRuntimeMetadataReferences()
+    {
+        return CachedRuntimeReferences.Value;
+    }
+
+    private static ImmutableArray<MetadataReference> CreateRuntimeMetadataReferences()
     {
         var trustedPlatformAssemblies = ((string?)AppContext.GetData("TRUSTED_PLATFORM_ASSEMBLIES"))?
                                         .Split(Path.PathSeparator, StringSplitOptions.RemoveEmptyEntries)

GFramework.SourceGenerators.Tests/Cqrs/CqrsHandlerRegistryGeneratorTests.cs

@@ -1,7 +1,6 @@
 using System.Reflection;
 using GFramework.SourceGenerators.Cqrs;
 using GFramework.SourceGenerators.Tests.Core;
-using Microsoft.CodeAnalysis.CSharp;
 
 namespace GFramework.SourceGenerators.Tests.Cqrs;
 
@@ -1155,7 +1154,11 @@ public class CqrsHandlerRegistryGeneratorTests
         var compilationErrors = updatedCompilation.GetDiagnostics()
             .Where(static diagnostic => diagnostic.Severity == DiagnosticSeverity.Error)
             .ToArray();
-        Assert.That(compilationErrors, Is.Empty, string.Join(Environment.NewLine, compilationErrors));
+        Assert.That(
+            compilationErrors,
+            Is.Empty,
+            () =>
+                $"编译生成的代码时出现错误:{Environment.NewLine}{string.Join(Environment.NewLine, compilationErrors.Select(static diagnostic => diagnostic.ToString()))}");
 
         var runResult = driver.GetRunResult();
         Assert.That(runResult.Results, Has.Length.EqualTo(1));