Allow reordering/pinning of session groups in the sidebar

Summary

Add a way to manually reorder (or pin) the groups of sessions shown in the left sidebar of the Claude Code desktop app.

Current behavior

Sessions are grouped by project in the left sidebar, and the groups appear to be ordered automatically (by recent activity). There is no way to control the order of the groups:

• No drag-and-drop reordering of groups
• No pin-to-top / favorite for a group
• Nothing in config.json or the app preferences that maps to group order (the per-session metadata is stored as individual JSON files and the grouping/order is derived at runtime)

Why this would help

People who keep several long-running projects open end up with the group they care about most jumping around as activity changes. A stable, user-controlled order makes the sidebar much easier to navigate.

Proposed options (any one would help)

• Drag-and-drop to reorder groups
• Pin / favorite a group so it stays at the top
• A sort toggle (e.g. manual / alphabetical / most-recent)

Environment

• Claude Code desktop app
• macOS