feat: 添加UnifiedOutputConverter到合并工具包，更新__all__导出列表

merger/__init__.py

@@ -8,6 +8,7 @@ from .text_matcher import TextMatcher
 from .bbox_extractor import BBoxExtractor
 from .data_processor import DataProcessor
 from .markdown_generator import MarkdownGenerator
+from .unified_output_converter import UnifiedOutputConverter
 
 __all__ = [
     'MinerUPaddleOCRMerger',
@@ -15,5 +16,6 @@ __all__ = [
     'TextMatcher',
     'BBoxExtractor',
     'DataProcessor',
-    'MarkdownGenerator'
+    'MarkdownGenerator',
+    'UnifiedOutputConverter',
 ]