[BUG] Sidebar sessions/projects disappeared from Code tab, data still exists

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

**Describe the bug**
All sessions/projects disappeared from the left sidebar in the Claude Code desktop app (Code tab). Previously had multiple projects and sessions visible, including grouped sessions. Now the sidebar shows nothing.

**What I've tried**
- Followed the troubleshooting guide — issue persists
- Restarted the app fully
- Checked for active filters/search in the sidebar
- Checked account/workspace selection

**Notable detail**
The sessions are NOT actually lost — I confirmed via the session-management tools (list_sessions) that all sessions still exist server-side (none archived or deleted), across multiple projects and custom sidebar groups, with activity dating back several months. So this looks like a sidebar rendering/sync bug rather than data loss.

**Expected behavior**
Sidebar should display existing sessions and groups as before.

**Environment**
- OS: Windows 11
- Claude Code desktop app (Code tab)

**Additional context**
Happy to provide more diagnostic info if useful, but withholding specific project names/paths here for privacy.

### What Should Happen?

I should see the historic project on thje left bar, they disappeared but claude code "found them", just not visually on the left bar.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

[bugreport.md](https://github.com/user-attachments/files/32297390/bugreport.md)

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

1.0.123

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_

Start with the attached bugreport.md and reproduce the empty sidebar in the Claude Code desktop app, checking the Code tab against the session-management list_sessions results. Compare behavior on the reported Claude Code 1.0.123 environment and verify that existing projects, sessions, and custom groups appear in the sidebar without being archived or deleted.

Written by the indexing model from the issue text.