Add AG-UI Blazor sample

dotnet/samples/AGUIDojo/AGUIDojoClient/Components/Demos/PredictiveStateUpdates/DocumentState.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Text.Json.Serialization;
+
+namespace AGUIDojoClient.Components.Demos.PredictiveStateUpdates;
+
+/// <summary>
+/// Represents the document state for the Predictive State Updates demo.
+/// This model mirrors the server-side DocumentState and is updated via streaming state updates.
+/// </summary>
+public sealed class DocumentState
+{
+    /// <summary>
+    /// Gets or sets the document content in Markdown format.
+    /// </summary>
+    [JsonPropertyName("document")]
+    public string Document { get; set; } = string.Empty;
+}