Cannot switch Ctrl+E focus between parallel running SubAgents

[yiliang114]

Background

PR #3721 introduced an isFocused gate on the SubAgent keyboard shortcut listener (AgentExecutionDisplay) to prevent parallel running SubAgents from toggling in lock-step (dual-reflow flicker). The fix for #3763 restored Ctrl+E for normal running SubAgents by falling back to the first running SubAgent when no confirmation is pending.

Problem

When multiple SubAgents run in parallel, only the first (by array order) receives Ctrl+E / Ctrl+F keyboard focus. The user has no way to switch focus to the second SubAgent — its display stays permanently in compact mode until it completes.

This is a design limitation inherited from #3721's single-focus approach. The current priority:

pending confirmation > first running SubAgent > none

Expected behavior

The user should be able to expand/collapse any running SubAgent, not just the first one. Possible approaches:

1. Focus cycling shortcut — e.g., Ctrl+Tab or similar to rotate keyboard focus among running SubAgents
2. Allow all running SubAgents to respond — accept the minor flicker tradeoff
3. Index-based shortcuts — e.g., Ctrl+1/2/3 to focus a specific SubAgent

Related

• ctrl+e / ctrl+f shortcuts do not expand running agent display #3763 — ctrl+e/ctrl+f shortcuts do not expand running agent display (fixed the single-agent case)
• fix(cli): bound SubAgent display by visual height to prevent flicker #3721 — fix(cli): bound SubAgent display by visual height to prevent flicker (introduced the focus gate)