Desktop app (Microsoft Store install) left headless after stealth update: no window until Store delivers the package

## Summary

On a Microsoft Store (MSIX) install of the Claude desktop app on Windows, the idle-time "stealth update" routine tears down the app window in preparation for a relaunch, but the process never exits or relaunches. The app is left running headless, with no window and nothing in the taskbar, until the Store delivers the new package (which kills the process) or the user ends it from Task Manager. In this instance the app was invisible for about 12.5 hours.

## Environment

- Claude desktop app 1.52386.3 (updated to 1.52386.6 when the Store finally delivered it), installed from the Microsoft Store (`[CCD-autoupdate] Disabled: MSIX install`, `[updater] MSIX detected: windowsStore=true`)
- Claude Code (bundled CLI) 2.1.266 at the time, 2.1.270 after the update
- Windows 10 Pro 22H2, build 19045, x64

## Timeline (from `%LOCALAPPDATA%\Claude\logs\main.log`)

Saturday evening, app idle:

```
19:49:13 [updater] Staged version 1.52386.6 is still current (latest: 1.52386.6, lastTarget: null)
19:49:42 [stealth-update] Triggering stealth update after idle timeout
19:49:42 [popout-restore] Saving 0 session + 0 pane + 0 project popout(s) for next launch
19:49:42 [stealth-relaunch] Saved z-order anchor: ...
19:49:42 [stealth-relaunch] Saved navigation history (11 entries, active=10)
19:49:43 [remote-tools-device] close
19:49:43 [CCD] Killing 1 PTY process tree(s) on quit
19:49:43 beforeQuitForUpdate handler fired, going down for update
```

No exit follows. The same process keeps logging all night (hourly growthbook refresh, per-minute `[process-memory]` samples showing the same main process and renderer PIDs, ~600 MB). It retries once:

```
19:59:43 [stealth-update] Triggering stealth update after idle timeout
```

again with no exit and no relaunch.

Monday morning, user clicks the taskbar icon twice:

```
08:24:44 Media permission probe / Blocked permission check (geolocation) ... <- a new renderer appears inside the old process, no visible window
08:25:11 Starting app
08:25:11 Not main instance, returning early from app ready <- second launch defers to the headless instance
08:25:11 [stealth-relaunch] Loaded z-order anchor: ...
```

Still no window. Then the Store installs the staged package, which terminates the old process, and the new version starts normally:

```
08:26:18 (AppXDeploymentServer) Deployment Register operation ... Claude_1.52386.6.0 ... finished successfully
08:26:27 Starting app
08:26:28 [updater] Version changed since last launch: 1.52386.3 -> 1.52386.6
```

No crash: nothing in Windows Application log (no 1000/1002), no WER 1001 entry, no Crashpad report.

## Expected

Either the stealth update exits and relaunches the app, or, on MSIX installs where the app cannot replace itself, it does not tear the UI down at all (or restores it when the relaunch cannot proceed).

## Actual

The UI is torn down, the process stays alive without a window, and clicking the app icon does not bring a window back (`Not main instance, returning early`). The app looks crashed/hung to the user.

## Workaround

End the Claude process tree in Task Manager and launch again. Sessions and transcripts survive.

## Notes

- The two-click pattern (`08:24:44` renderer created, `08:25:11` second instance deferring) may be useful to reproduce: a headless instance still holds the single-instance lock.
- Earlier "hangs" on this machine (Windows Event 1002 entries within a minute of `[stealth-update]` lines) look like the same path.