No way to unarchive a session (only workspace.archiveSession exists)

[shengbuding]

Summary

In dsh 0.1.0-rc.6, the workspace layer only exposes archive for sessions (workspace.archiveSession) — there is no unarchive counterpart anywhere in the RPC registry or the UI. A session archived by accident cannot be restored through any supported path.

Steps to reproduce

1. Open the dsh web UI, archive any session (e.g. from the sidebar).
2. Try to restore it — there is no unarchive action in the UI, and the API registry has no reverse operation.

Impact

• The archived session's data is fully preserved on disk (the archive never touches the session artifacts), but the session disappears from every grouping view and cannot be brought back.
• The only recovery path is to stop the server, hand-edit $DSH_HOME/storages/workspace.json (remove the id from global.archivedSessionIds), and restart. That is fragile and unfriendly for a GUI feature with an accidental-click profile.

Code references

• @deepseek-ai/dsh-workspace exposes only archiveSession(sessionId) (the Workspace domain class and the workspace.archiveSession RPC). The RPC registry has exactly: workspace.list / create / rename / delete / insertBefore / insertSessionBefore / archiveSession.
• The storage comment already anticipates restoration: "an archived session keeps its sessionIds slot (unarchiving must restore the…)" — so the design intent is there; only the operation is missing.

Suggested fix

• Add workspace.unarchiveSession (symmetric: remove the id from archivedSessionIds, restoring visibility in all groupings).
• Surface it in the UI — e.g. an "archived sessions" section with a restore action, or a restore entry in the session menu.

dsh version: 0.1.0-rc.6 (npm @deepseek-ai/dsh).