The collapsed sidebar renders agent rows with an unconditional
Style::default().fg(p.overlay0), so the active agent is
indistinguishable from the others. The workspace list directly above
it, and render_agent_detail in the expanded sidebar, both mark the
active entry.
Reuse the existing active treatment: resolve the active entry with the
same is_active_pane call the expanded agent panel uses, then paint the
row background with surface_dim and the position number with text, the
same tokens the collapsed workspace rows already use.
Assisted-By: devx/717e5259-915f-4a7b-af07-6abe46da5b90