Segmented Control in WPF XAML ISLAND, XAML parsing failed.

### Describe the bug

Hello,

When I add
```xmlns:controls="using:CommunityToolkit.WinUI.Controls"```
And
```

```
To StackPanel, the Window does not initialize anymore with cryptic error: XAML parsing failed.

I think the issue is how I initialize resources:
```
protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
{
XamlControlsXamlMetaDataProvider.Initialize();
xamlMetaDataProvider = new();
this.Resources.MergedDictionaries.Add(new Microsoft.UI.Xaml.Controls.XamlControlsResources());
//this.Resources.MergedDictionaries.Add(new Microsoft.UI.Xaml.ResourceDictionary() { Source = new Uri("ms-appx:///CommunityToolkit.WinUI.Controls.Segmented/Themes/Generic.xaml") });

}
```
If I uncomment my attempt to load Segmented, it fails on COM Exception.

### Steps to reproduce

https://github.com/castorix/WPF_XAML_Islands_WinUI3/tree/master

Clone this repo, update to newest WinUI SDK, add CommunityToolkit.WinUI.Segmented and add Segmented. Same issue.

### Expected behavior

Segmented loads?

### Screenshots

_No response_

### Code Platform

- [ ] UWP
- [x] WinAppSDK / WinUI 3
- [ ] Web Assembly (WASM)
- [ ] Android
- [ ] iOS
- [ ] MacOS
- [ ] Linux / GTK

### Windows Build Number

- [ ] Windows 10 1809 (Build 17763)
- [ ] Windows 10 1903 (Build 18362)
- [ ] Windows 10 1909 (Build 18363)
- [ ] Windows 10 2004 (Build 19041)
- [ ] Windows 10 20H2 (Build 19042)
- [ ] Windows 10 21H1 (Build 19043)
- [ ] Windows 10 21H2 (Build 19044)
- [x] Windows 10 22H2 (Build 19045)
- [ ] Windows 11 21H2 (Build 22000)
- [ ] Other (specify)

### Other Windows Build number

_No response_

### App minimum and target SDK version

- [ ] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [x] Windows 10, version 2004 (Build 19041)
- [ ] Windows 10, version 2104 (Build 20348)
- [ ] Windows 11, version 22H2 (Build 22000)
- [ ] Other (specify)

### Other SDK version

_No response_

### Visual Studio Version

_No response_

### Visual Studio Build Number

2026 Version: 18.0.0

### Device form factor

Desktop

### Additional context

It is WPF XAML ISLANDS.

### Help us help you

Yes, I'd like to be assigned to work on this item.

Klone die verknüpfte WPF_XAML_Islands_WinUI3-Reproduktion und beginne mit OnLaunched, dem Segmented-XAML-Element und der in der Issue gezeigten Ressourceninitialisierung. Vergleiche das Verhalten mit und ohne das Segmented-Ressourcenwörterbuch und bestätige, was die XAML-Parsing- oder COM-Ausnahme verursacht. Als abgeschlossen gilt die Aufgabe, wenn Segmented in der angegebenen WPF-XAML-Islands-Konfiguration geladen wird, ohne die Initialisierung von Window zu verhindern.

Vom Indexierungsmodell aus dem Issue-Text verfasst.