Fold all agents in one space

[Yoni-Erlich]

The grouped agent list shows every agent from every space at once. With many agents open, the sidebar gets messy: long stacks of names, lots of scrolling, and it is hard to see which space I actually care about.

When one space has several agents, I have to scroll past all of them to reach the others. I want to fold or unfold all agents that belong to the same space, and fold or unfold every space at once, so unused agents stay out of the way.

macOS 14.5, Herdr 0.8.0, Ghostty.