[BUG] Trust settings couldn't be saved on Windows after update to 1.3883.0

Version: 1.3883.0 (Windows MSIX)
OS: Windows 11

Description:
After updating to 1.3883.0, clicking "Trust Workspace" shows error
"Trust settings couldn't be saved" and app is completely blocked.
This worked fine before the update.

Root cause suspected:
CodexSandboxUsers group has only RX permission on .claude.json —
cannot write trust settings after update reset file permissions.

hasTrustDialogAccepted is already true in .claude.json but app still blocks.

Steps to reproduce:

1. Update Claude Desktop to 1.3883.0 on Windows
2. Open any workspace (previously trusted or new)
3. Click "Trust Workspace"
4. See error: "Trust settings couldn't be saved"
5. App is completely blocked, cannot proceed

Expected: Trust is saved, app proceeds normally
Actual: App blocked completely