feat(05-01): add KB_INTERMEDIATE_PATH config to KBSettings

- Add intermediate_path field with default ~/work/intermediate/analysis/
- Follow pydantic-settings naming convention for env var override
- Users can customize via KB_INTERMEDIATE_PATH environment variable

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

kb_pipeline/config.py

@@ -37,6 +37,10 @@ class KBSettings(BaseSettings):
     # 必需配置
     base_path: str = Field(..., description="知识库根目录")
     archive_path: str = Field(..., description="归档目录")
+    intermediate_path: str = Field(
+        default_factory=lambda: str(Path.home() / "work" / "intermediate" / "analysis"),
+        description="中间文件存储目录"
+    )
 
     # 可选配置
     git_root: str = Field(default="", description="Git 仓库根目录")