shu/do not raise TargetClosedError in cleanup

[wintonzheng]

• do not raise TargetClosedError in task cleanup when target has been closed
• better error handling: make sure browser clean up won't raise error that breaks other cleanup progress (like artifact upload)

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[!IMPORTANT] Improve error handling in task cleanup by logging and handling exceptions without raising TargetClosedError in agent.py, browser_factory.py, and browser_manager.py.

• Error Handling:
  • In agent.py, cleanup_browser_and_create_artifacts() now includes a note to handle exceptions gracefully without raising them.
  • In browser_factory.py, close() method now logs and handles exceptions during browser context and Playwright closure.
  • In browser_manager.py, cleanup_for_task() and cleanup_for_workflow_run() now log errors instead of raising them during cleanup.

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