Add 'Mark as Completed' option for agent sessions

I’d like the ability to mark agent sessions as “completed” for better organization.

Current behavior: The context menu for agent sessions includes Pin, Duplicate, Mark as Unread, Delete, and Rename options.

Requested behavior: Add a “Mark as Completed” option that visually distinguishes finished sessions from ongoing work. This could:

  • Add a checkmark icon or subtle styling to completed sessions
  • Optionally allow filtering by completed/active status
  • Provide a way to toggle between completed/active states

Use case: When working on multiple tasks throughout the day, it’s helpful to track which agent sessions represent finished work vs. tasks still in progress. Currently, I have to mentally track this or delete sessions I might want to reference later.

This would complement the existing “Mark as Unread” option nicely.