[FEATURE] Desktop sidebar: show running sessions in a section on top while keeping Group by: Project

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

In the desktop app's Code tab sidebar, there is no way to see running sessions together while keeping the project view:

• Group by: Project: running sessions are spread across the project groups.
• Group by: State: running sessions are together, but the project view is gone.
• A custom "Recent" group: a session can only appear in one place, so filing it under "Recent" takes it out of its project group. Custom sections also aren't shown while Group by is Project.
• Pinning: same problem. Pinned sessions are shown only under Pinned, detached from their project (#90145).

Proposed Solution

Add an automatic "Running / Recent" section at the top of the sidebar. It would show running or recently active sessions in addition to their normal place in the project groups, as a mirror rather than a move. The project groups underneath stay unchanged.

Alternative Solutions

Let each sidebar section have its own Group by setting (sections already store group_by / sort_by, but it has no visible effect yet). Then one section could use Group by State, filtered to running, above a section that uses Group by Project.

Priority

Medium - Would be very helpful

Feature Category

Other (Desktop app sidebar)

Use Case Example

I work across several repos (about 5 project folders and 100+ sessions), often with a few sessions running in parallel in different projects. I want to see at a glance which sessions are running right now without losing the per-project view I use to find older sessions.

Additional Context

Related: #83699 (collapsed project groups should still show active sessions), #90145 (pinning detaches a session from its group).