[BUG] Desktop (Windows): all custom sidebar groups wiped after usage-limit pause/resume, no app restart

Environment

• Claude desktop app for Windows (Store/MSIX package Claude_pzs8sxrjxfjjc), app_version seen in local storage: 2.31226.0
• Windows 11 Pro 10.0.26200
• Date: 2026-10-10, around 20:20 KST

What happened

1. I had the Code tab sidebar organized into several custom groups, with sessions filed under them.
2. I hit my usage limit, so all running sessions stopped.
3. When the limit lifted and sessions resumed, every custom group was gone. The app was NOT closed or restarted in between.
4. All sessions themselves still exist (22 including archived), but every one is now ungrouped.
5. Fully quitting and relaunching the app did not bring the groups back.

Expected
Custom groups and session-to-group assignments survive a usage-limit pause/resume.

What the local state shows

• Local Storage key dframe-store (origin https://claude.ai) now contains

"customGroupsByScope":{"<account>/<org>":{"groups":[],"assignments":{},"order":{}}}
while "groupByByMode":{"code":"custom"} is still set — i.e. the "group by custom groups" view setting survived, but the group data was overwritten with an empty value.

• "pendingLegacyGroupMigration":null, and codeSidebarByScope has "migratedFrom":1,"prefsSeeded":true.
• dframe-store.backup.v1 only holds an old-format empty value ("customGroups":[]), so there is nothing to restore from.
• LSS-persisted.dframe-group-scopes = {}.
• logs/main.log has not been written since 2026-06-02, so I could not find the moment of the reset in logs.

Impact
Manual sidebar organization is lost with no way to recover it; it has to be rebuilt by hand.

Requests

• Fix whatever rehydration/migration path writes an empty customGroupsByScope over existing data.
• Keep a real backup of the previous sidebar state before overwriting it.

Possibly related
#79810, #65669, #86843, #79184 (same symptom, different triggers)