[Requests and ideas] Better support/organization for HIGH session counts.

### Feature summary

Add better organization for sessions. Perhaps project sub-groups and terminal/session tiling

### What problem are you trying to solve?

As a power user, I often have 15+ sessions active at once. I need a way to better organize them. I'm aware that I can color-code them, but that's very manual and requires me to 1) remember to do it and, 2) remember what a color represents.

Example sessions:
Per repo (and I often have 2-3 repos each with this):
- 2-3 for active and draft PRs
- 1-3 for parallel work
- 1-4 for assisting in PR reviews
- 1-2 for general questions

This is literally the only feature preventing me from switching to Copilot.

### Proposed solution

I currently use https://github.com/paulallington/Claudes. It's main benefit is being able to tile sessions on one screen:

Each cell can be maximized and minimized. You can drag to resize rows and columns as needed.

However, I've also forked it so that I can give "workspaces" to each project/repo:

Each workspace has a separate layout of terminals.

I'm not sure exactly what this would look like in Copilot. TBH, if it had these two exact features I would be very happy.

### Workflow impact

This would allow me to:
1. Easily monitor and steer multiple sessions at once
2. Easily context shift between different groups of sessions
3. It's much easier to leave a session and come back to it when needed, IMO

### Installation context

_No response_

### Additional context

_No response_