Added a way to read what the AI received from your sources (#1100)

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

app/MindWork AI Studio/Tools/Services/Indexing/EmbeddingChunk.cs

@@ -1,14 +1,27 @@
 namespace AIStudio.Tools.Services.Indexing;
 
 /// <summary>
-/// One chunk as the chunking produced it, together with the page it starts on.
+/// One chunk as the chunking produced it, together with where it starts and where it ends.
 /// </summary>
 /// <remarks>
-/// The page is carried rather than read back out of the chunk text. The runtime states it, and
-/// the chunking knows which source segment a chunk begins in, so nothing has to be derived from
-/// a marker in the text — which is what used to leave Word files and continued passages without
-/// a page.
+/// The locations are carried rather than read back out of the chunk text. The runtime states them,
+/// and the chunking knows which source segments a chunk covers, so nothing has to be derived from a
+/// marker in the text — which is what used to leave Word files and continued passages without a
+/// page.
 /// </remarks>
 /// <param name="Text">The chunk itself, overlap prefix included.</param>
-/// <param name="PageNumber">The page the chunk's own content starts on, or null when it has none.</param>
-internal sealed record EmbeddingChunk(string Text, int? PageNumber);
+/// <param name="Start">Where the chunk's own content starts: its page, its sheet and row, or its line.</param>
+/// <param name="End">Where the chunk ends. Equal to the start when the chunk stays within one page, row or line.</param>
+/// <param name="AttachmentPosition">Which attachment of a mail the chunk is from, counted from zero as the index numbers them, or null for the text of the mail itself and for anything but a mail.</param>
+internal sealed record EmbeddingChunk(string Text, SourceLocation Start, SourceLocation End, int? AttachmentPosition = null)
+{
+    /// <summary>
+    /// The page the chunk's own content starts on, or null when it has none.
+    /// </summary>
+    public int? PageNumber => this.Start.PageNumber;
+
+    /// <summary>
+    /// The page the chunk ends on, or null when it has none.
+    /// </summary>
+    public int? EndPageNumber => this.End.PageNumber;
+}