fix: 修复JSON解析错误导致的"Unexpected end of JSON input"问题

- 移除express.json()的verify函数中危险的buffer修改逻辑
- 该逻辑直接修改body-parser正在处理的原始buffer，导致数据损坏
- 改进JSON解析错误中间件，支持更多错误模式识别
- 将内部500错误改为用户友好的400错误响应
- 修复了Claude CLI客户端连接时的JSON解析问题

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/app.js

@@ -141,55 +141,33 @@ class Application {
             if (buf && buf.length && !buf.toString(encoding || 'utf8').trim()) {
               throw new Error('Invalid JSON: empty body')
             }
-
-            // Unicode 字符清理 - 清理无效的 UTF-16 代理对
-            if (buf && buf.length) {
-              try {
-                const str = buf.toString(encoding || 'utf8')
-                // 移除无效的 UTF-16 代理对字符
-                const cleanedStr = str.replace(
-                  /[\uDC00-\uDFFF](?![\uD800-\uDBFF])|[\uD800-\uDBFF](?![\uDC00-\uDFFF])/g,
-                  '\uFFFD'
-                )
-
-                // 如果字符串被清理过，重新写入buffer
-                if (cleanedStr !== str) {
-                  logger.warn('🧹 Cleaned invalid Unicode characters from request body')
-                  const cleanedBuf = Buffer.from(cleanedStr, encoding || 'utf8')
-                  // 将清理后的内容复制回原buffer
-                  cleanedBuf.copy(buf, 0)
-                  // 调整buffer长度
-                  buf._charsWritten = cleanedBuf.length
-                }
-              } catch (error) {
-                logger.warn(
-                  '⚠️ Unicode cleaning failed, proceeding with original buffer:',
-                  error.message
-                )
-              }
-            }
+            // 注意：不在这里修改buffer，避免导致JSON解析错误
           }
         })
       )
       this.app.use(express.urlencoded({ extended: true, limit: '10mb' }))
 
-      // 🧹 Unicode 错误处理中间件
+      // 🧹 JSON 解析错误处理中间件
       this.app.use((err, req, res, next) => {
         if (err instanceof SyntaxError && err.status === 400 && 'body' in err) {
-          // 检查是否是Unicode相关的JSON解析错误
+          // JSON 解析错误统一处理
+          logger.warn('🚨 JSON parsing error detected:', err.message)
+          
+          // 检查是否是常见的JSON解析错误
           if (
+            err.message.includes('Unexpected end of JSON input') ||
+            err.message.includes('Unexpected token') ||
+            err.message.includes('Expected property name') ||
+            err.message.includes('in JSON at position') ||
             err.message.includes('surrogate') ||
             err.message.includes('UTF-16') ||
             err.message.includes('invalid character')
           ) {
-            logger.warn('🧹 Detected Unicode JSON parsing error, attempting recovery:', err.message)
-
             return res.status(400).json({
               type: 'error',
               error: {
                 type: 'invalid_request_error',
-                message:
-                  'The request body contains invalid Unicode characters. Please ensure your text uses valid UTF-8 encoding and does not contain malformed surrogate pairs.'
+                message: 'Invalid JSON format in request body. Please ensure the request contains valid JSON data.'
               }
             })
           }