Persist permanent indexing failures in the RAG index

app/MindWork AI Studio/Tools/Services/DataSourceEmbeddingManifest.cs

@@ -11,4 +11,15 @@ public sealed class DataSourceEmbeddingManifest
     public int VectorSize { get; set; }
 
     public Dictionary<string, EmbeddedFileRecord> Files { get; init; } = new(StringComparer.OrdinalIgnoreCase);
+
+    /// <summary>
+    /// The files whose indexing failed for a reason which lies in the file itself, keyed by their
+    /// absolute path.
+    /// </summary>
+    /// <remarks>
+    /// These files are not read again as long as their fingerprint stays the same. Without this,
+    /// a folder holding hundreds of scanned documents without a text layer would be read again on
+    /// every single run, with the outcome known in advance.
+    /// </remarks>
+    public Dictionary<string, PermanentIndexingFailureRecord> PermanentFailures { get; init; } = new(StringComparer.OrdinalIgnoreCase);
 }

app/MindWork AI Studio/Tools/Services/PermanentIndexingFailureRecord.cs

@@ -0,0 +1,3 @@
+namespace AIStudio.Tools.Services;
+
+public sealed record PermanentIndexingFailureRecord(string Fingerprint, FileExtractionErrorCode Code, string Message, DateTimeOffset OccurredAtUtc);