Making agent pane more mouse friendly

[hamza-usmani]

Description of the new feature

I should be able to click the turns/output in the agent pane with a mouse. For example, the arrows to expand and collapse:

I should be able to click a session in the session management UI with mouse, as well as when a command is being suggested to run or insert.

Proposed technical implementation details

No response

[yeelam-gordon]

We investigate on this before, it cannot be easily fixed. We need to do it post initial release.

REASON: Since mouse event handling once turn on, we need to implement every operation ourselves, including mouse highlight, right click, left click at where and what to do.
Now, we can "feel" the mouse is working NOT because we did any thing on it, it is because terminal will automatically handle above operation for us, and it aligned with mouse event in TUI aspect.

Another REASON:
github copilot cli also doesn't handle mouse event as well.

Last reason:
That TUI is keyboard driven rather than mouse driven.