Auto Settle: hide a running thread and settle silently when done

[Pawel-Kica]

I often give an agent a task with a clear outcome, like saving a document to my desktop or running a long job, and don't need to review its final reply. I'd like to clear it from my sidebar immediately without stopping the work or coming back to settle it manually.

An Auto Settle action, perhaps /auto-settle, could work like this:

• Enable it for an individual conversation, including while the agent is running.
• Hide the conversation from the active sidebar immediately and let the agent keep working.
• Settle it automatically when the work finishes, without a completion notification or bringing it back into the sidebar.
• Keep the conversation accessible with other settled threads.

The name and exact interaction are flexible. The useful part is being able to say "finish this and put it away" upfront.

Related: #9942 proposes agent-controlled settlement. This request adds a user-controlled action that hides the thread while it is still running and makes completion silent.

[Pawel-Kica]