Added the visual briefing assistant (#893)

app/MindWork AI Studio/Assistants/VisualBriefing/VisualBriefingPreparedSources.cs

@@ -0,0 +1,54 @@
+using AIStudio.Chat;
+
+namespace AIStudio.Assistants.VisualBriefing;
+
+/// <summary>
+/// Holds prepared source inputs and owns their temporary optimized attachment files.
+/// </summary>
+internal sealed class VisualBriefingPreparedSources : IAsyncDisposable
+{
+    /// <summary>
+    /// Gets or initializes the temporary directory.
+    /// </summary>
+    internal string TemporaryDirectory { get; init; } = string.Empty;
+
+    /// <summary>
+    /// Gets or initializes model attachments.
+    /// </summary>
+    internal IReadOnlyList<FileAttachment> Attachments { get; init; } = [];
+
+    /// <summary>
+    /// Gets or initializes transcript sections keyed by stable source ID.
+    /// </summary>
+    internal IReadOnlyDictionary<Guid, string> Transcripts { get; init; } = new Dictionary<Guid, string>();
+
+    /// <summary>
+    /// Gets or initializes prepared visual assets.
+    /// </summary>
+    internal IReadOnlyDictionary<string, PreparedVisualBriefingAsset> Assets { get; init; } = new Dictionary<string, PreparedVisualBriefingAsset>(StringComparer.Ordinal);
+
+    /// <summary>
+    /// Gets or initializes the current source fingerprint.
+    /// </summary>
+    internal string SourceFingerprint { get; init; } = string.Empty;
+
+    /// <summary>
+    /// Deletes temporary optimized attachment files on a best-effort basis.
+    /// </summary>
+    /// <returns>A completed value task.</returns>
+    public ValueTask DisposeAsync()
+    {
+        try
+        {
+            if (!string.IsNullOrWhiteSpace(this.TemporaryDirectory) &&
+                Directory.Exists(this.TemporaryDirectory))
+                Directory.Delete(this.TemporaryDirectory, recursive: true);
+        }
+        catch
+        {
+            // Temporary optimized visual assets are cleaned up best effort.
+        }
+        
+        return ValueTask.CompletedTask;
+    }
+}