feat(browser_toolset): enhance error handling and connection management

- Introduced BrowserToolError for tool-level errors, ensuring they don't trigger sandbox recreation.
- Implemented connection caching for Playwright in BrowserToolSet, optimizing resource usage.
- Enhanced _run_in_sandbox method to differentiate between infrastructure and tool-level errors, improving error handling.
- Added unit tests for error handling and connection management in BrowserToolSet.

This update improves the robustness of the browser toolset by refining error handling and optimizing Playwright connection management.

Signed-off-by: Sodawyx <sodawyx@126.com>

Author: Sodawyx