Feature request: show pane IDs in the UI (sidebar / pane borders)

[honbolau]

Summary

There is currently no way to display a pane's ID (e.g. w1:p1) in the Herdr UI. It would be very useful to be able to see pane IDs directly in the interface, since pane IDs are the primary way to target panes/agents via the CLI (herdr pane run <pane_id>, herdr agent prompt <pane_id> ..., etc.).

Current behavior

• The sidebar Agent rows support tokens like state_icon, workspace, tab, pane, agent, terminal_title, but the pane token renders the manual pane label (pane rename), not the pane ID.
• Pane border titles show: terminal title → manual label → agent label (show_agent_labels_on_pane_borders), never the pane ID.
• There is no config option like show_pane_ids in the default config.

So the only way to know a pane's ID is to run herdr pane list / herdr agent list from a shell.

Proposed solutions (any of these would be great)

1. Sidebar token: Add a built-in sidebar token (e.g. pane_id) that renders the public pane ID (e.g. w4:p11) in Agent rows, configurable via ui.sidebar.agents.rows.
2. Pane border title: Include the pane ID in the pane border title (e.g. as a fallback when no manual label is set, or via a config flag like show_pane_ids_on_pane_borders).
3. Pane menu / context menu: Show the pane ID in the right-click pane menu, or add a "Copy pane ID" action.

Use case

When coordinating multiple agents/panes (e.g. spawning sibling panes via the CLI and targeting them later), it's common to need the pane ID while looking at the UI — e.g. to tell an agent "send that prompt to pane X" or to verify which pane ID corresponds to which agent.

Workaround today

Manually label panes with their ID:

herdr pane rename w4:p11 "w4:p11"

or report a metadata token and render it with a $name sidebar token.

[honbolau]

Related threads on the same need — linking them so they can be considered together:

• [idea] show_pane_id_on_pane_borders #715 [idea] show_pane_id_on_pane_borders (June 21) — same request, including a suggestion for a right-click Copy pane ID action
• Quick way to copy current pane ID without interrupting running processes? #1880 Quick way to copy current pane ID without interrupting running processes (July 28) — workflow pain point behind wanting pane IDs visible/copyable
• Focus a specific pane by its ID #1086 Focus a specific pane by its ID — related, targets panes by ID from the UI

This seems to be a recurring need (at least three separate threads), so any of the proposed options (sidebar token, pane border, menu action) would help.