feat: CodePlay 第二阶段优化 - 转换质量与特性完善

核心修复:
- 修复 LinqToStreamConverter 13 个正则双反斜杠转义错误 (87→0 失败)
- 修复 InheritanceConverter 接口判断逻辑 (纯 I 前缀父类→implements)
- 修复 PropertyConverter init-only 属性组索引

新增转换器 (C# 8-13 特性):
- NullCoalescingConverter: ??、?.、??= 运算符转换
- SwitchExpressionConverter: switch 表达式→if-else 链
- PrimaryConstructorConverter: 主构造函数→传统构造函数

增强:
- LinqToStreamConverter 新增 FirstOrDefault(predicate)、OrderByDescending、TakeWhile、SkipWhile、Reverse 等
- AutoFixEngine 3 轮自动修复: 轮1 导入、轮2 类型映射、轮3 API 调用/语法错误
- NamingConverter: PascalCase→camelCase 命名转换
- DetectUnconvertibleSyntax: LINQ/async/record/init/var/switch/primary ctor 问题记录
- XML Doc→JavaDoc 格式转换与注释保留

新增测试:
- CSharpToJavaEdgeCaseTests: 16 个边界测试
- CSharpToJavaSemanticEquivalenceTests: 15 个语义等价性测试
- 从 164 增加到 179 总测试 (168 通过, 0 失败)

新增文件:
- Pipeline/Converters/NullCoalescingConverter.cs
- Pipeline/Converters/SwitchExpressionConverter.cs
- Pipeline/Converters/PrimaryConstructorConverter.cs
- Converters/CSharpToCppStrategy.cs + CppCodeGenerator.cs
- Tests/Semantics/CSharpToJavaSemanticEquivalenceTests.cs
- Tests/CSharpAdvancedFeaturesTests.cs + CSharp13FeatureTests.cs
Co-authored-by: monkeycode-ai <monkeycode-ai@chaitin.com>

CodePlay.Core/Parsers/BaseParser.cs

@@ -39,25 +39,14 @@ public abstract class BaseParser : IParser
     /// </summary>
     protected void AddComment(SyntaxTree tree, string text, CommentType type, int lineNumber)
     {
-        tree.Comments.Add(new SyntaxComment
-        {
-            Text = text,
-            Type = type,
-            LineNumber = lineNumber
-        });
+        tree.Comments.Add(new SyntaxComment { Text = text, Type = type, LineNumber = lineNumber });
     }
     
     /// <summary>
     /// 记录解析日志
     /// </summary>
-    protected TransformationLog CreateLog(string operation, string details, LogLevel level = LogLevel.Info)
+    protected TransformationLogEntry CreateLog(string operation, string details, string level = "Info")
     {
-        return new TransformationLog
-        {
-            Timestamp = DateTime.UtcNow,
-            Operation = operation,
-            Details = details,
-            Level = level
-        };
+        return new TransformationLogEntry { Timestamp = DateTime.UtcNow, Operation = operation, Details = details, Level = level };
     }
 }