[idea] Let plugins add a sidebar section (or group workspaces under a header)

[timofurrer]

idea / problem

I run a few "workstreams" in herdr: each is a coordinator agent plus several worker agents, spread across worktrees of more than one repo. Today the only way to make that visible is ordering workspaces with workspace.move_block and putting a $stream token into the Spaces rows via workspace.report_metadata. That works, but there's no way to show where one group ends and the next begins.

requested change

One of these:

• a plugin-provided sidebar section next to Spaces and Agents, with rows the plugin reports (label, state icon, a target workspace or pane to focus on select), or
• a first-class workspace group: workspace.group.set with a name, rendered as a collapsible header in Spaces.

The second one is probably the smaller change and fits the existing model, since groups would only be presentation, like the metadata tokens. I'm aware native non-terminal plugin UI is out of scope for plugin v1, so I'm not sure which of the two fits your roadmap better 🤔

why you want this

I'd see at a glance which agents belong to which workstream and jump straight to the coordinator, without a popup or custom ordering scripts that fight the default layout. Happy to help with the implementation if you think this is worth having.

[wenhanweime]

I'm not a Herdr maintainer, so I can't say which of the two fits the roadmap. But the "which agents belong to which workstream" problem is one I run into a lot, so here is how I'd look at it.

Of your two options, the workspace group header sounds like the smaller and safer one. It only changes how things are drawn, and it fits how the metadata tokens already work. A plugin-owned sidebar section is a bigger step, and you already noted that's outside plugin v1.

One thing a header can't do by itself: a workstream usually has a goal, something it's blocked on, and a next step. Those live in your head (or in notes) and not on the row. Even with a nice group header, you still have to open the coordinator to remember where the workstream stopped.

Disclosure: I'm the author of Herduck (https://github.com/wenhanweime/herduck, early open-source alpha). It runs next to Herdr and doesn't change the sidebar. You create a "Work" and attach sessions from different folders or repos to it, and each Work holds a goal / status / blocker / next step. That is close to your coordinator + workers across several worktrees case. It does not give you a collapsible header inside Herdr's Spaces list, and it doesn't jump to a pane for you. So it covers the "where did this workstream stop" part, not the "see it at a glance in the sidebar" part.

If you try it and it doesn't fit how you run your workstreams, I'd like to hear what's missing.