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/Views/Tabs/StorageView.xaml.cs

@@ -1,4 +1,7 @@
 using System.Windows.Controls;
+using LiveChartsCore;
+using LiveChartsCore.Kernel;
+using LiveChartsCore.Kernel.Sketches;
 
 namespace SharepointToolbox.Views.Tabs;
 
@@ -8,5 +11,43 @@ public partial class StorageView : UserControl
     {
         InitializeComponent();
         DataContext = viewModel;
+
+        StoragePieChart.Tooltip = new SingleSliceTooltip();
+    }
+}
+
+/// <summary>
+/// Custom tooltip that only shows the single closest/hovered pie slice
+/// instead of LiveCharts2's default which shows multiple nearby slices.
+/// </summary>
+internal sealed class SingleSliceTooltip : IChartTooltip
+{
+    private readonly System.Windows.Controls.ToolTip _tip = new()
+    {
+        Padding = new System.Windows.Thickness(8, 4, 8, 4),
+        FontSize = 13,
+        Background = new System.Windows.Media.SolidColorBrush(
+            System.Windows.Media.Color.FromRgb(255, 255, 255)),
+        BorderBrush = new System.Windows.Media.SolidColorBrush(
+            System.Windows.Media.Color.FromRgb(200, 200, 200)),
+        BorderThickness = new System.Windows.Thickness(1),
+    };
+
+    public void Show(IEnumerable<ChartPoint> foundPoints, Chart chart)
+    {
+        // Only show the first (closest) point
+        var point = foundPoints.FirstOrDefault();
+        if (point == null) { Hide(chart); return; }
+
+        var label = point.Context.Series.GetPrimaryToolTipText(point);
+        if (string.IsNullOrEmpty(label)) label = point.Context.Series.Name ?? "";
+
+        _tip.Content = label;
+        _tip.IsOpen = true;
+    }
+
+    public void Hide(Chart chart)
+    {
+        _tip.IsOpen = false;
     }
 }