fix(06-03): remove sys.path manipulation from zhihu_extractor.py

- Remove unnecessary sys.path.insert for current directory
- Use pure relative import for markdown_converter
- Package imports work correctly without path manipulation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

kb_workflow/metadata/zhihu_extractor.py

@@ -4,20 +4,11 @@
 """
 
 import re
-import sys
 import os
 from typing import Dict, Optional, Any
 from urllib.parse import urlparse
 
-# 添加当前目录到 Python 路径以支持绝对导入
-current_dir = os.path.dirname(os.path.abspath(__file__))
-if current_dir not in sys.path:
-    sys.path.insert(0, current_dir)
-
-try:
-    from .markdown_converter import MarkdownConverter
-except ImportError:
-    from markdown_converter import MarkdownConverter
+from .markdown_converter import MarkdownConverter
 
 
 class PlaywrightBrowser: