Improved docx and odt import (#890)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/DocumentManager.cs

@@ -0,0 +1,61 @@
+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 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.currentPageContent = new StringBuilder();
+
+            //
+            // Sections, not pages: a Word or OpenDocument file carries no fixed page layout, so the
+            // runtime derives these boundaries from page breaks and heuristics. Calling them pages,
+            // as the PDF reader does with its real ones, would invite the AI to cite page numbers
+            // which do not exist in the document.
+            //
+            this.currentPageContent.AppendLine($"# Section {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 markdownImage = ContentStreamSseHandler.BuildImageMarkdown(image.Id, image.MediaType);
+            if (markdownImage is not null)
+            {
+                this.currentPageContent.AppendLine();
+                this.currentPageContent.AppendLine(markdownImage);
+            }
+        }
+
+        return null;
+    }
+
+    public string? Flush()
+    {
+        if (this.currentPageContent is null)
+            return null;
+
+        var result = this.currentPageContent.ToString();
+        this.currentPageContent = null;
+        return string.IsNullOrWhiteSpace(result) ? null : result;
+    }
+}