Dear Maintainer,

Installing `gnome-shell-extension-prefs` version `51~alpha-3` on Debian testing (Forky) with GNOME Shell 50 installed causes APT to remove the working GNOME desktop environment.

### Steps to reproduce

On a system with `gnome-shell` version `50.5-1` installed, run:

```sh
sudo apt install gnome-shell-extension-prefs
```

APT proposes to install `gnome-shell-extension-prefs` version `51~alpha-3` and `gnome-extensions-app`, while removing 21 packages, including:

- `gnome-shell`
- `gnome-session`
- `gnome-shell-common`
- `gnome-shell-extensions`
- `gnome-tweaks`
- `gnome-classic`
- `gnome-shell-extension-manager`
- numerous GNOME Shell extensions

The transaction was accepted on my system on 26 October 2026. Following the subsequent `apt autoremove` and a reboot, GNOME was no longer available in the display manager's session list. I had to reinstall `gnome-session` and `gnome-shell`, and subsequently reinstall `gnome-shell-extensions` and `gnome-tweaks`, to restore my desktop.

I have since reproduced the proposed removal transaction using APT's dependency resolution, without accepting it again.

The package candidate is `51~alpha-3`, while the installed GNOME Shell version is `50.5-1`. This appears to be related to the ongoing GNOME Shell 51 transition (see Debian bug #1150014).

### Expected behaviour

Installing an extension-management utility should not unexpectedly remove the working desktop environment. If this package requires GNOME Shell 51, its availability in testing should be coordinated with the transition so that users running GNOME Shell 50 are not offered a transaction that removes their desktop.

### Actual behaviour

APT resolves the installation by removing GNOME Shell, GNOME Session, GNOME Tweaks and numerous extensions, leaving GNOME unavailable after reboot.

Please investigate whether the package's dependencies and its migration into testing are appropriate while GNOME Shell 50 remains the installed version there.