refactor(06-01): update platform adapters to use standard imports

- Remove sys.path manipulation from bilibili.py and zhihu.py
- Use standard imports from kb_workflow.metadata
- Remove try/except wrappers around imports

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

kb_pipeline/platforms/zhihu.py

@@ -11,17 +11,11 @@ from typing import Dict, Any, Optional
 from datetime import datetime
 import re
 import asyncio
-import sys
-from pathlib import Path
-
-# Add kb-zhihu-metadata to path for import
-_kb_zhihu_path = Path(__file__).parent.parent.parent / "kb-zhihu-metadata"
-if str(_kb_zhihu_path) not in sys.path:
-    sys.path.insert(0, str(_kb_zhihu_path))
 
 from kb_pipeline.platforms.base import PlatformAdapter
 from kb_pipeline.errors import AuthError
 from kb_pipeline.config import get_settings
+from kb_workflow.metadata.zhihu_extractor import ZhihuPlaywrightExtractor
 
 
 class ZhihuAdapter(PlatformAdapter):
@@ -89,24 +83,15 @@ class ZhihuAdapter(PlatformAdapter):
     def _get_extractor(self):
         """Get or create ZhihuPlaywrightExtractor instance.
 
-        Lazy import to avoid dependency issues when kb-zhihu-metadata is not installed.
-
         Returns:
             ZhihuPlaywrightExtractor instance
         """
         if self._extractor is None:
-            try:
-                from zhihu_extractor import ZhihuPlaywrightExtractor
-                self._extractor = ZhihuPlaywrightExtractor(
-                    headless=self.headless,
-                    timeout=self.timeout,
-                    cookie=self.cookie
-                )
-            except ImportError as e:
-                raise ImportError(
-                    "kb-zhihu-metadata module not found. "
-                    "Please ensure kb-zhihu-metadata directory exists."
-                ) from e
+            self._extractor = ZhihuPlaywrightExtractor(
+                headless=self.headless,
+                timeout=self.timeout,
+                cookie=self.cookie
+            )
         return self._extractor
 
     def _extract_with_playwright(self, url: str) -> Optional[Dict[str, Any]]: