Split panes/tiling

### Feature summary

Add a way to split the main pane and see multiple chats simultaneously

### What problem are you trying to solve?

Working with multiple agents at the same time, seeing their progress in parallel, and trandferring between them easily

### Proposed solution

Multiple panes and tiling, like in text editor like vscode

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_