[idea] reposition the agent panel to a new right sidebar.

[WeiXu94]

idea / problem

Now both the workspace and agent list live in the left sidebar. I want that we can move the agent list panel to a new right sidebar since sometimes I may have a lot of workspaces or agents opening at the same time and then have to scroll to see all of them or switch to another one.

requested change

• add a config to set the position of each panel.
• adjust the position via mouse drag/keybinding/menu.

why you want this

I can do a demo and then you may review it.