Name the preselected data sources that cannot be used right now

app/MindWork AI Studio/Components/DataSourceSelection.razor.cs

@@ -181,6 +181,22 @@ public partial class DataSourceSelection : MSGComponentBase
         var preselectedDataSourceIds = this.DataSourceOptions.PreselectedDataSourceIds.ToHashSet(StringComparer.Ordinal);
         return this.GetConfiguredDataSourcesSnapshot().Where(ds => preselectedDataSourceIds.Contains(ds.Id)).ToList();
     }
+
+    /// <summary>
+    /// Names the preselected data sources which the filters removed.
+    /// </summary>
+    /// <remarks>
+    /// This list shows what survived the filters, while the preselection keeps what the user asked
+    /// for. Without this, a preselected source which cannot be used right now is simply missing
+    /// from the list, and nothing says so. Preselected ids without a configured source are left
+    /// out: that source is gone, not unavailable.
+    /// </remarks>
+    /// <returns>The names of the unusable preselected data sources, or an empty string when there are none.</returns>
+    private string GetUnavailablePreselectedDataSourceNames()
+    {
+        var availableDataSourceIds = this.availableDataSources.Select(ds => ds.Id).ToHashSet(StringComparer.Ordinal);
+        return string.Join(", ", this.GetDataSourcesFromConfiguredIds().Where(ds => !availableDataSourceIds.Contains(ds.Id)).Select(ds => ds.Name));
+    }
     
     private async Task LoadAndApplyFilters()
     {