fix: add session cleanup to AgentDelegationTool

[tortmayr]

What it does

Cleanup the session created by the AgentDelegationTool after the tool invocation has completed i.e. the response from the newly created session has been received.

Fixes #15995

How to test

Follow the instructions of #15995

Observe that when clicking the Show Chats button any temp session that as been created by the AgentDelegationTool is no longer visible i.e. has been removed successfully.

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[sdirix]

Personally I think it would be cleaner if these sessions are never added to the shown sessions in the first place. Do you think this would be easily possible?

[tortmayr]

Personally I think it would be cleaner if these sessions are never added to the shown sessions in the first place. Do you think this would be easily possible?

I agree.
Unfortunately we currently have no way to distinguish between "real" sessions and nested/delegated sessions created by the AgentDelegationTool. So I don't see an easy way to filter them out.
Even if we would manage to only show "real" sessions, we still have to cleanup the secondary session once the tool invocation is completed.
So I don't think there is any harm in merging this.

And then work on improvements in a follow-up.

There is also another open Issue mentioned in a FIX-ME comment in the code that should be tackled.

[tortmayr]

I have created a follow-up ticket in: #16000