added a DocumentManager.cs to buffer only the active document page and its images

app/MindWork AI Studio/Tools/DocumentManager.cs

@@ -0,0 +1,58 @@
+using System.Text;
+
+namespace AIStudio.Tools;
+
+/// <summary>
+/// Buffers only the active document page so that its image segments can follow
+/// the page Markdown without retaining the complete document in memory.
+/// </summary>
+public sealed class DocumentManager
+{
+    private int currentPageNumber;
+    private StringBuilder? currentPageContent;
+
+    public string? AddPage(ContentStreamDocumentMetadata metadata, string? content, bool extractImages)
+    {
+        var pageNumber = metadata.Document?.PageNumber ?? 0;
+        if (pageNumber == 0)
+            return content;
+
+        var image = metadata.Document?.Image;
+        if (image is null)
+        {
+            var completedPage = this.Flush();
+            this.currentPageNumber = pageNumber;
+            this.currentPageContent = new StringBuilder();
+            this.currentPageContent.AppendLine($"# Page {pageNumber}");
+            this.currentPageContent.Append(content);
+            return completedPage;
+        }
+
+        if (!extractImages || this.currentPageContent is null || string.IsNullOrWhiteSpace(image.Id))
+            return null;
+
+        if (ContentStreamSseHandler.ProcessImageSegment(image.Id, image))
+        {
+            var base64 = ContentStreamSseHandler.BuildImage(image.Id);
+            if (!string.IsNullOrWhiteSpace(base64))
+            {
+                var mediaType = string.IsNullOrWhiteSpace(image.MediaType) ? "image/jpeg" : image.MediaType;
+                this.currentPageContent.AppendLine();
+                this.currentPageContent.AppendLine($"![Image](data:{mediaType};base64,{base64})");
+            }
+        }
+
+        return null;
+    }
+
+    public string? Flush()
+    {
+        if (this.currentPageContent is null)
+            return null;
+
+        var result = this.currentPageContent.ToString();
+        this.currentPageContent = null;
+        this.currentPageNumber = 0;
+        return string.IsNullOrWhiteSpace(result) ? null : result;
+    }
+}