Show what happens to the data sources while they are re-indexed (#979)

app/MindWork AI Studio/Tools/Databases/IndexStore/DataSourceIndexState.cs

@@ -0,0 +1,19 @@
+namespace AIStudio.Tools.Databases.IndexStore;
+
+/// <summary>
+/// What the index knows about a data source as a whole, without its files.
+/// </summary>
+/// <remarks>
+/// The manifest answers the same question, but reads every file and every stored failure of the
+/// data source to do so. That is the right thing before a run, and far too much for a question
+/// asked about several data sources every time somebody opens the data source selection.
+///
+/// SourceHash is the telling one: it is written once a run has worked through the whole data
+/// source, and resetting the index deletes the row it lives in. So an empty hash means no run has
+/// finished since the index was last discarded.
+/// </remarks>
+/// <param name="EmbeddingProviderId">The embedding provider the stored vectors were created with.</param>
+/// <param name="EmbeddingSignature">Identifies the embedding configuration the stored vectors belong to.</param>
+/// <param name="SourceHash">The hash of the data source as a whole, written when a run completes.</param>
+/// <param name="VectorSize">The dimension of the stored vectors.</param>
+public sealed record DataSourceIndexState(string EmbeddingProviderId, string EmbeddingSignature, string SourceHash, int VectorSize);