Desktop/Web: sidebar group membership is device-local while Group by/Sort by syncs — make group assignment account state

What happens

Sessions sync across devices, and per #94262 the sidebar's Group by and Sort by preferences also sync to the account. But which group a session belongs to does not. It lives only on the machine where it was set, in %APPDATA%\Claude\claude_desktop_config.json under preferences.epitaxyPrefs["dframe-group-scopes"].

Open the same account on a second machine and the sessions are all there — every one of them Ungrouped.

Why this is worth revisiting

The split is the confusing part: half of the grouping feature is account state, and the half that carries the user's actual filing work is not. Nothing in the UI suggests that dragging a session into a group is a device-local act.

Consequences already reported here:

• groups lost after an app update — #79134
• creating a new group overwrote every existing one (dframe-group-scopes replaced instead of merged) — #86843
• users hand-editing the Electron config to carry their grouping to another machine

Steps to reproduce

1. On machine A, create a sidebar group and drag a few sessions into it.
2. Open Claude Code on machine B, signed in to the same account.
3. The sessions are listed; the group is gone and they show as Ungrouped.

Ask

Store group membership as account state alongside the sessions themselves. Failing that, a documented export/import of dframe-group-scopes — so the workaround is not hand-editing an internal config file — plus a note in the desktop docs that grouping is per-device, since today nothing says so.

Prior reports

#65177 and #61553 describe the same gap from the web and multi-window angles. Both were closed as not planned without discussion, so filing fresh rather than commenting on closed threads.