Added material to the BeyondFacts Lab (#1180)

app/MindWork AI Studio/Assistants/BeyondFactsLab/BflMaterialEntry.cs

@@ -0,0 +1,14 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// A material in the list of a preparation, also when it cannot be opened.
+/// </summary>
+/// <param name="MaterialId">The ID of the material.</param>
+/// <param name="Material">The material, or null when its files are damaged or missing, or a newer version of AI Studio stored it.</param>
+public sealed record BflMaterialEntry(Guid MaterialId, BflMaterial? Material)
+{
+    /// <summary>
+    /// Gets whether the material can be opened.
+    /// </summary>
+    public bool IsAvailable => this.Material is not null;
+}