fix: update error types for upstream errors and JSON marshal failure

dto/claude.go

@@ -488,14 +488,14 @@ func (c *ClaudeResponse) GetClaudeError() *types.ClaudeError {
 	case string:
 		// 处理简单字符串错误
 		return &types.ClaudeError{
-			Type:    "error",
+			Type:    "upstream_error",
 			Message: err,
 		}
 	default:
 		// 未知类型，尝试转换为字符串
 		return &types.ClaudeError{
-			Type:    "unknown_error",
-			Message: fmt.Sprintf("%v", err),
+			Type:    "unknown_upstream_error",
+			Message: fmt.Sprintf("unknown_error: %v", err),
 		}
 	}
 }