chore: archive v1.1 Enhanced Reports milestone

v1.1 shipped with 4 phases (25 plans), 10/10 requirements complete:
- Global site selection (toolbar picker, all tabs consume)
- User access audit (Graph people-picker, direct/group/inherited)
- Simplified permissions (plain-language labels, risk levels, detail toggle)
- Storage visualization (LiveCharts2 pie/donut + bar charts)

Post-phase polish: centralized site selection (removed per-tab pickers),
claims prefix stripping, StorageMetrics backfill, chart tooltip fix,
summary stats in app + HTML exports.

205 tests passing, 10,484 LOC.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

SharepointToolbox/Services/Export/StorageCsvExportService.cs

@@ -36,7 +36,49 @@ public class StorageCsvExportService
     public async Task WriteAsync(IReadOnlyList<StorageNode> nodes, string filePath, CancellationToken ct)
     {
         var csv = BuildCsv(nodes);
-        // UTF-8 with BOM for Excel compatibility
+        await File.WriteAllTextAsync(filePath, csv, new UTF8Encoding(encoderShouldEmitUTF8Identifier: true), ct);
+    }
+
+    /// <summary>
+    /// Builds a CSV with library details followed by a file-type breakdown section.
+    /// </summary>
+    public string BuildCsv(IReadOnlyList<StorageNode> nodes, IReadOnlyList<FileTypeMetric> fileTypeMetrics)
+    {
+        var sb = new StringBuilder();
+
+        // Library details
+        sb.AppendLine("Library,Site,Files,Total Size (MB),Version Size (MB),Last Modified");
+        foreach (var node in nodes)
+        {
+            sb.AppendLine(string.Join(",",
+                Csv(node.Name),
+                Csv(node.SiteTitle),
+                node.TotalFileCount.ToString(),
+                FormatMb(node.TotalSizeBytes),
+                FormatMb(node.VersionSizeBytes),
+                node.LastModified.HasValue
+                    ? Csv(node.LastModified.Value.ToString("yyyy-MM-dd"))
+                    : string.Empty));
+        }
+
+        // File type breakdown
+        if (fileTypeMetrics.Count > 0)
+        {
+            sb.AppendLine();
+            sb.AppendLine("File Type,Size (MB),File Count");
+            foreach (var m in fileTypeMetrics)
+            {
+                string label = string.IsNullOrEmpty(m.Extension) ? "(no extension)" : m.Extension;
+                sb.AppendLine(string.Join(",", Csv(label), FormatMb(m.TotalSizeBytes), m.FileCount.ToString()));
+            }
+        }
+
+        return sb.ToString();
+    }
+
+    public async Task WriteAsync(IReadOnlyList<StorageNode> nodes, IReadOnlyList<FileTypeMetric> fileTypeMetrics, string filePath, CancellationToken ct)
+    {
+        var csv = BuildCsv(nodes, fileTypeMetrics);
         await File.WriteAllTextAsync(filePath, csv, new UTF8Encoding(encoderShouldEmitUTF8Identifier: true), ct);
     }