[FEATURE] Desktop: option to keep Code sidebar Group by / Sort by on this device only (opt out of account sync)

### Preflight Checklist

- [x] I have searched [existing requests](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20label%3Aenhancement) and this feature hasn't been requested yet
- [x] This is a single feature request (not multiple features)

### Problem Statement

In the desktop app's Code tab, the sidebar's **Group by** and **Sort by** choices sync to my account. I use several laptops with the same account, and I want a different sidebar layout on each one. Right now I can't: whatever I pick on one laptop overwrites the others.

Some sidebar settings already stay on the device (folder group order, collapsed groups, the Status and Environment filters, the Last activity days filter). Group by and Sort by don't, even though they describe how *this screen* should look, not account data. There is no setting to change that.

### Proposed Solution

A setting (for example Settings > Claude Code > "Sync sidebar view settings across devices", on by default) that, when turned off, keeps **Group by** and **Sort by** on this device only:

- Changes made on this device are not uploaded.
- Changes made on other devices are not applied here.
- Pins and custom groups could keep syncing, or get their own toggle.

A per-setting "this device only" option inside the sidebar's filter menu would work just as well.

### Alternative Solutions

- **Same settings on every laptop:** avoids the conflict but defeats the point; I want them different.
- **Local Storage flags:** the obvious ones don't help. Setting `ccd-sync-quarantine`, or changing `ccd-sync-owner`, makes the app reset the local view settings and adopt the server copy on next launch.
- **Blocking the sync request:** that would mean intercepting HTTPS traffic, which isn't reasonable for a view preference.
- **Patching the app bundle:** breaks the code signature and is undone by every update.

### Priority

Medium - Would be very helpful

### Feature Category

Configuration and settings

### Use Case Example

1. On my main laptop I want Group by: Folder, Sort by: Last activity, because I switch between many projects there.
2. On a second laptop used for a few long-running sessions, I want Group by: Date.
3. I set the second laptop to Date. The next time I open the app on the main laptop, it has also switched to Date.
4. With a per-device option, each laptop would keep its own layout.

### Additional Context

What I observed in Claude desktop **1.52386.3** on macOS 26.6.2 (arm64), from the shipped (minified) sidebar code, so details may change:

- **Synced store:** the sidebar store is uploaded to `PUT /api/claude_code/organizations//user_settings` under the entry `ccd/dframe-store`.
- **Synced keys:** `groupByByMode`, `sortByByMode`, `pinnedOrder`, `homeProjectsPinnedOrder`, `recentsTypeFilter`, `recentsStatusFilter`, `coworkActivityDays`, `routinesSidebarPlacement`, `navPinnedIds`, plus custom groups.
- **Server wins:** when the app reconciles with the server, the server's `groupByByMode` and `sortByByMode` override the local values.
- **Local-only settings, for contrast:** `code-projects-order`, `code-sessions-status-filter`, `code-sessions-environment-filter`, `code-sessions-state-activity-days`, `code-sessions-show-empty-projects`, and `code-sessions-show-pr-status` are stored per install and never uploaded. The split between the two groups looks accidental from a user's point of view.

Related, but different:

- #92038: show only this device's sessions (about which sessions are listed, not view settings)
- #92717: groups don't sync to mobile (asks for *more* sync of groups)
- #78812: sync engine resetting groups on account switch

Start by tracing the desktop sidebar store entry `ccd/dframe-store`, its reconciliation behavior, and the `PUT /api/claude_code/organizations//user_settings` path described in the issue. Compare the synced keys with the listed local-only settings and define whether the toggle applies to Group by and Sort by only; done means device-specific choices no longer upload or get overwritten while default sync remains available.

索引モデルが issue の本文から書いたものです。