PWA apps open as a new Chrome window instead of a standalone app

### Overview

When a PWA is installed and launched from the desktop, it opens as a new window within the main Google Chrome application instance, rather than running as a separate, standalone application. This behavior prevents the PWA from being treated as a distinct app by the desktop environment (e.g., in the dock or taskbar).

### Steps to Reproduce

1. Install Google Chrome from Flathub.
2. Navigate to a website that can be installed as a PWA (e.g., `app.spotify.com`, `twitter.com`, or `youtube.com`).
3. Click the "Install" icon in the address bar to add the PWA to your desktop.
4. Close all Google Chrome windows.
5. Launch the newly created PWA from your desktop's application menu or shortcut.

### Expected Behavior

The PWA should launch in its own window, with its own application icon in the dock/taskbar, and be treated as a separate application by the operating system. It should not be grouped with the main Google Chrome browser icon.

### Actual Behavior

The PWA opens as a new window under the main Google Chrome application icon. The window title is correct, but the app is not sandboxed as a standalone instance. It is treated simply as another Chrome window.

### System Information

* **OS:** Fedora Linux 42 (Workstation Edition)
* **Desktop Environment:** GNOME 48 on Wayland
* **Flatpak Version:** Flatpak 1.16.1
* **Chrome Version:** 140.0.7339.207-1 stable

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