BrowserSessionManager

Manages browser sessions for different threads.

This class maintains separate browser sessions for different threads, enabling concurrent usage of browsers in multi-threaded environments. Browsers are created lazily only when needed by tools.

Concurrency protection is also implemented. Each browser session is tied to a specific thread_id and includes protection against concurrent usage. When a browser is obtained via get_async_browser() or get_sync_browser(), it is marked as "in use", and subsequent attempts to access the same browser session will raise a RuntimeError until it is released. In general, different callers should use different thread_ids to avoid concurrency issues.