Bug: Weird windows vista like title bar

### Reproduction steps

open Grayjay on Fedora Workstation 42 or 43

### Actual result

Title bar not corresponding

to GNOME dark theme. Screenshot:

### Expected result

A window title bar suited to GNOME dark theme

### Flatpak info

Grayjay - Universal media aggregator

ID: app.grayjay.Grayjay
Ref: app/app.grayjay.Grayjay/x86_64/stable
Arch: x86_64
Branch: stable
Version: 12
License: LicenseRef-Source-First-1.1=https://github.com/futo-org/Grayjay.Desktop/blob/master/LICENSE.md
Origin: flathub
Collection: org.flathub.Stable
Installation: system
Installed: 607.6 MB
Runtime: org.freedesktop.Platform/x86_64/24.08
Sdk: org.freedesktop.Sdk/x86_64/24.08

Commit: 6cd97bc742fed9f6a9e8e3caced673d52cf30647049609fca8cc12bb180ab3a3
Parent: 19ce68567c82fb38ff89d4ce3109925e5428946eb431022520f16fd2a4684d2e
Subject: Merge pull request #37 from flathub/v12 (76d7ac609f05)
Date: 2025-10-29 14:08:32 +0000

### What plugins are you seeing the problem on?

Youtube

### Plugin Version

300

### Which OS version are you using?

Fedora workstation 43

### When do you experience the issue?

- [ ] While logged in
- [ ] While logged out
- [x] N/A

### Are you using a VPN?

No

### References

_No response_

### Relevant log output

```shell

```

Reproduce Grayjay from the Flatpak details on Fedora Workstation 43 with the GNOME dark theme; the issue names no source file, test, or entry point. Trace the desktop window/title-bar handling from the application entry point. Done means the title bar matches the GNOME dark theme while the reported Youtube setup remains usable.

Written by the indexing model from the issue text.