Animation.Repeat property set to Forever plays only once

### Describe the bug

I tried to use a repeating animation but it seems to only play once, ignoring the `Forever` option being set.

### Steps to reproduce

This is all you need as code to reproduce the issue:

```XAML

```

### Expected behavior

I would expect the `Forever` value for the `Repeat` property to loop the animation until is stopped.

### 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)
- [ ] Windows 10 22H2 (Build 19045)
- [ ] Windows 11 21H2 (Build 22000)
- [x] Other (specify)

### Other Windows Build number

26200.8117

### App minimum and target SDK version

- [x] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [ ] 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

18.4.3

### Device form factor

Desktop

### Additional context

I tested with `CommunityToolkit.WinUI.Behaviors` version **8.3.260402-preview2** and stable version **8.2.251219**.

### Help us help you

No, I'm unable to contribute a solution.

Beginne damit, das von StartAnimationAction verwendete Verhalten von Animation.Repeat und ScalarAnimation nachzuverfolgen, und suche dann nach vorhandenen Animationstests oder Beispielen, die Wiederholungsanzahlen abdecken. Reproduziere den XAML-Fall in einem WinAppSDK/WinUI 3-Beispiel und überprüfe, dass Repeat="Forever" weiterläuft, bis die Animation gestoppt wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.