对齐 docs 和代码里 storage config 的 workspace 属性

[myysy]

Description

对齐 docs 和代码里 storage config 的 workspace 属性

Related Issue

#287

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

变更了一些 docs 目录的文档

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes

[CLAassistant]

All committers have signed the CLA.

[qin-ctx]

1. VLM 字段名错误（严重）：文档写的 base_url，代码实际是 api_base（VLMConfig 使用 extra:
   "forbid"，用户按文档配置会报错）
2. AGFS timeout 默认值错误：文档写 30.0，代码实际默认 10
3. AGFS backend 枚举过时：文档写 local|remote，代码实际支持 local|s3|memory
4. 缺失新参数文档：补充了 vlm.thinking、vlm.max_concurrent、embedding.max_concurrent 参数说明

还有这几个代码和文档不一致的问题，一起修复下？