dsh-session-grove: Add cross-workspace session grouping to the DSH sidebar.

dsh-session-grove is a sidebar plugin for DSH Desktop maintained by momijijin. It introduces a Free Groups layer atop the native Workspace view, enabling sessions from different workspaces to coexist within the same group. Deliberately, it avoids modifying workspace assignment, registry, session logs, or the workspace.json file. This article details the boundaries, installation methods via dshmarket, compatibility constraints for engines.dsh >=0.2.0-rc.2 <0.3.0, group and session operations, search and archive states, data storage locations, manual upgrade path from dsh-session-groups, as well as important notes for the beta phase: The plugin operates with the host dsh process's permissions; users should verify the source code and LICENSE prior to installation. Real DSH UI functionality has only been verified on Windows, while Linux/macOS support remains experimental, and Beta and NEXT desktop shells are explicitly not supported.