[Bug] Auto-update fails with Permission denied on WSL2 .deb installation

[Nza6920]

Description

The built-in updater fails with the following error when Codex Switcher is installed system-wide from the Debian package inside WSL2:

Update failed: Permission denied (os error 13)

Environment

• Host OS: Windows 11, build 26200.9168, x64
• Runtime: WSL2 with WSLg
• WSL distribution: Ubuntu 24.04.3 LTS (Noble Numbat), x86_64
• WSL kernel: 6.6.87.2-microsoft-standard-WSL2
• Installation method: Debian package (.deb), installed system-wide
• Installed package: codex-switcher 0.2.9 amd64
• Executable: /usr/bin/codex-switcher
• Available update: v0.2.11
• Codex CLI: codex-cli 0.149.1
• Codex Switcher is launched as a regular, non-root user through WSLg

Steps to reproduce

1. Install Codex Switcher v0.2.9 from the .deb release package in Ubuntu running under WSL2.
2. Launch Codex Switcher as a regular user through WSLg.
3. Accept the in-app update to v0.2.11.
4. The update download starts, but installation fails.

Actual behavior

The updater shows:

Update failed: Permission denied (os error 13)

The application remains on v0.2.9.

Expected behavior

The updater should either:

1. successfully update a system-wide .deb installation using an appropriate privilege flow, or
2. detect that the executable is managed by a system package and show clear instructions to update by downloading/installing the new .deb package instead of attempting to overwrite /usr/bin/codex-switcher as an unprivileged user.

Additional context

The exact error is shown in the attached/local screenshot. Account identifiers have been redacted. The failure appears consistent with the updater attempting to replace a root-managed executable while the application is running as a regular user.