.NET 9 Partial Properties For Sample Options

### Describe the bug

Would be nice to convert to something like:

```cs
[ToolkitSample(...)]
public sealed partial class MySample : Page
{
[ToolkitSampleNumericOption(min: 0.0, max: 1.0)]
public partial double MyRangeValue { get; set; } = 0.5;
}
```

This can make it clearer to see the properties in the code-behind (and use them there) as well.

### Steps to reproduce

```text
N/A
```

### Expected behavior

N/A

### Screenshots

_No response_

### Code Platform

- [ ] UWP
- [ ] 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 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)
- [ ] Windows 10, version 2004 (Build 19041)
- [ ] Other (specify)

### Other SDK version

_No response_

### Visual Studio Version

_No response_

### Visual Studio Build Number

_No response_

### Device form factor

_No response_

### Additional context

_No response_

### Help us help you

Yes, but only if others can assist.

Start by locating the existing ToolkitSample and ToolkitSampleNumericOption definitions and how sample option properties are currently handled. Determine the scope of converting them to C# partial properties, then verify that the sample code can declare the shown syntax and that the generated options retain their current behavior.

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