文件系统访问

Initial release with secure workspace file access:

- Enables safe local file read, write, and list functions within the OpenClaw workspace directory.
- Access is limited to relative paths or workspace subdirectories to prevent unauthorized file operations.
- Write operations outside the workspace are strictly prohibited.
- Intended use cases: viewing logs, generating reports, saving scripts or configuration files.
- Users are advised not to delete important files such as configuration, source code, or system files.