Support C# partial properties for [Notify]

[RoccoZero]

Hi! I would like to request support for C# partial properties in PropertyChanged.SourceGenerator.

Currently [Notify] works by annotating backing fields:

[Notify]
private string theme = "System";

This generates a public Theme property, which is useful for normal INotifyPropertyChanged scenarios.

However, this pattern does not work well with other source generators, especially System.Text.Json source generation for NativeAOT. The generated property is not visible to the System.Text.Json source generator in the same compilation, so the JSON contract cannot easily use the generated property.

It would be very useful to support a syntax like:

[Notify]
public partial string Theme { get; set; } = "System";

Expected generated behavior:

generate the property implementation
raise PropertyChanged
keep hooks such as OnThemeChanged(...)
allow attributes such as [JsonPropertyName], [JsonIgnore], etc. to be placed directly on the property
work better with NativeAOT and System.Text.Json source generation
Example use case:

[JsonSerializable(typeof(AppSettings))]
public partial class AppSettingsJsonContext : JsonSerializerContext;

public partial class AppSettings : INotifyPropertyChanged
{
   [Notify]
   public partial string Theme { get; set; } = "System";

   [Notify]
   public partial string ThemeColor { get; set; } = "Blue";
}

This would make the public properties part of the original source code, so other source generators can see them.

CommunityToolkit.Mvvm already supports this style, and it would be great to have similar support here without taking a dependency on the full MVVM Toolkit.

Thanks!