[FEATURE] Custom groups in the CLI agents view, like the desktop app

The desktop app lets me sort my agent sessions into my own custom groups. The CLI agents view (claude agents) doesn't — it's just one flat list.

I bounce between desktop and the terminal during the day. On desktop my fleet is grouped and tidy; in the CLI that's gone and I'm scanning everything again.

Would love for the CLI agents view to show the same custom groups I set up on desktop (ideally synced, so a session lands in the same group on both).

Today I just work around it with separate folders/tmux names, which doesn't really carry over between desktop and CLI.

(Found #60063 asking for something similar but it got closed, so opening a fresh one focused on desktop/CLI parity.)