Group menu bar sessions by project path

[Jing-yilin]

Summary

In the Perch macOS menu bar app, sessions are currently shown as one flat list. I would like pending sessions to be grouped by project path so it is easier to scan sessions when multiple projects are active.

Problem

When many sessions are parked, the menu bar list becomes hard to navigate because sessions from different projects are interleaved. Users often resume work by project first, then by session title.

Proposed behavior

• Group pending sessions by their working_dir / project path.
• Add a simple visual separator or section header for each project group.
• Use a concise project label, such as the last path component or a shortened path.
• Keep the existing Completed section behavior, or optionally apply the same grouping there later.
• Preserve existing session actions: copy resume command, mark done/reopen, delete.

Acceptance criteria

• Pending menu bar sessions are grouped by project path.
• Each group has a clear label or separator.
• Sessions within each group remain sorted by the existing sort order.
• Empty state and Completed section continue to work.
• No screenshots or private local paths are included in the public issue.