Feature/multi query stores dashboard overview

src/PlanViewer.App/Controls/QuerySessionControl.axaml

@@ -57,6 +57,11 @@
                             Height="28" Padding="8,0" FontSize="12"
                             Theme="{StaticResource AppButton}"
                             ToolTip.Tip="Analyze top queries from Query Store"/>
+                    <Button x:Name="QueryStoreOverviewButton" Content="&#x1F4CA; QS Overview"
+                            Click="QueryStoreOverview_Click"
+                            Height="28" Padding="8,0" FontSize="12"
+                            Theme="{StaticResource AppButton}"
+                            ToolTip.Tip="Query Stores Overview across all databases"/>
                     <TextBlock Text="|" VerticalAlignment="Center"
                                Foreground="{DynamicResource ForegroundBrush}" Margin="2,0"/>
                     <Button x:Name="CopyReproButton" Content="&#x1F4CB; Copy Repro"

src/PlanViewer.App/Controls/QuerySessionControl.axaml.cs

@@ -1389,6 +1389,161 @@ private bool HasQueryStoreTab()
 
     public void TriggerQueryStore() => QueryStore_Click(null, new RoutedEventArgs());
 
+    private async void QueryStoreOverview_Click(object? sender, RoutedEventArgs e)
+    {
+        if (_serverConnection == null || _connectionString == null)
+        {
+            await ShowConnectionDialogAsync();
+            if (_serverConnection == null || _connectionString == null)
+                return;
+        }
+
+        SetStatus("Loading Query Store Overview...");
+
+        var supportsWaitStats = _serverMetadata?.SupportsQueryStoreWaitStats ?? false;
+        var overview = new QueryStoreOverviewControl(_serverConnection, _credentialService,
+            supportsWaitStats: supportsWaitStats);
+        overview.DrillDownRequested += async (_, args) =>
+        {
+            // Open a single-database Query Store tab directly (no connection dialog)
+            _selectedDatabase = args.Database;
+            _connectionString = _serverConnection!.GetConnectionString(_credentialService, args.Database);
+            await OpenQueryStoreForDatabaseAsync(args.Database, args.StartUtc, args.EndUtc);
+        };
+
+        var headerText = new TextBlock
+        {
+            Text = "QS Overview",
+            VerticalAlignment = Avalonia.Layout.VerticalAlignment.Center,
+            FontSize = 12
+        };
+
+        var closeBtn = new Button
+        {
+            Content = "\u2715",
+            MinWidth = 22, MinHeight = 22, Width = 22, Height = 22,
+            Padding = new Avalonia.Thickness(0),
+            FontSize = 11,
+            Margin = new Avalonia.Thickness(6, 0, 0, 0),
+            Background = Brushes.Transparent,
+            BorderThickness = new Avalonia.Thickness(0),
+            Foreground = new SolidColorBrush(Color.FromRgb(0xE4, 0xE6, 0xEB)),
+            VerticalAlignment = Avalonia.Layout.VerticalAlignment.Center,
+            HorizontalContentAlignment = HorizontalAlignment.Center,
+            VerticalContentAlignment = VerticalAlignment.Center
+        };
+
+        var header = new StackPanel
+        {
+            Orientation = Avalonia.Layout.Orientation.Horizontal,
+            Children = { headerText, closeBtn }
+        };
+
+        var tab = new TabItem { Header = header, Content = overview };
+        closeBtn.Tag = tab;
+        closeBtn.Click += (s, _) =>
+        {
+            if (s is Button btn && btn.Tag is TabItem t)
+                SubTabControl.Items.Remove(t);
+        };
+
+        SubTabControl.Items.Add(tab);
+        SubTabControl.SelectedItem = tab;
+
+        try
+        {
+            await overview.LoadAsync();
+            SetStatus("");
+        }
+        catch (Exception ex)
+        {
+            SetStatus(ex.Message.Length > 80 ? ex.Message[..80] + "..." : ex.Message, autoClear: false);
+        }
+    }
+
+    private async Task OpenQueryStoreForDatabaseAsync(string database, DateTime? initialStartUtc = null, DateTime? initialEndUtc = null)
+    {
+        var connStr = _serverConnection!.GetConnectionString(_credentialService, database);
+
+        // Check if Query Store is enabled
+        SetStatus($"Checking Query Store on {database}...");
+        try
+        {
+            var (enabled, state) = await QueryStoreService.CheckEnabledAsync(connStr);
+            if (!enabled)
+            {
+                SetStatus($"Query Store not enabled on {database} ({state ?? "unknown"})");
+                return;
+            }
+        }
+        catch (Exception ex)
+        {
+            SetStatus(ex.Message.Length > 80 ? ex.Message[..80] + "..." : ex.Message, autoClear: false);
+            return;
+        }
+
+        SetStatus("");
+
+        // Check if wait stats are supported
+        var supportsWaitStats = _serverMetadata?.SupportsQueryStoreWaitStats ?? false;
+        if (supportsWaitStats)
+        {
+            try
+            {
+                supportsWaitStats = await QueryStoreService.IsWaitStatsCaptureEnabledAsync(connStr);
+            }
+            catch { supportsWaitStats = false; }
+        }
+
+        var databases = DatabaseBox.Items.OfType<string>().ToList();
+
+        var grid = new QueryStoreGridControl(_serverConnection!, _credentialService,
+            database, databases, supportsWaitStats);
+        if (initialStartUtc.HasValue && initialEndUtc.HasValue)
+            grid.SetInitialTimeRange(initialStartUtc.Value, initialEndUtc.Value);
+        grid.PlansSelected += OnQueryStorePlansSelected;
+
+        var headerText = new TextBlock
+        {
+            Text = $"Query Store — {database}",
+            VerticalAlignment = Avalonia.Layout.VerticalAlignment.Center,
+            FontSize = 12
+        };
+        grid.DatabaseChanged += (_, db) => headerText.Text = $"Query Store — {db}";
+
+        var closeBtn = new Button
+        {
+            Content = "\u2715",
+            MinWidth = 22, MinHeight = 22, Width = 22, Height = 22,
+            Padding = new Avalonia.Thickness(0),
+            FontSize = 11,
+            Margin = new Avalonia.Thickness(6, 0, 0, 0),
+            Background = Brushes.Transparent,
+            BorderThickness = new Avalonia.Thickness(0),
+            Foreground = new SolidColorBrush(Color.FromRgb(0xE4, 0xE6, 0xEB)),
+            VerticalAlignment = Avalonia.Layout.VerticalAlignment.Center,
+            HorizontalContentAlignment = HorizontalAlignment.Center,
+            VerticalContentAlignment = VerticalAlignment.Center
+        };
+
+        var header = new StackPanel
+        {
+            Orientation = Avalonia.Layout.Orientation.Horizontal,
+            Children = { headerText, closeBtn }
+        };
+
+        var tab = new TabItem { Header = header, Content = grid };
+        closeBtn.Tag = tab;
+        closeBtn.Click += (s, _) =>
+        {
+            if (s is Button btn && btn.Tag is TabItem t)
+                SubTabControl.Items.Remove(t);
+        };
+
+        SubTabControl.Items.Add(tab);
+        SubTabControl.SelectedItem = tab;
+    }
+
     private async void QueryStore_Click(object? sender, RoutedEventArgs e)
     {
         // If a QS tab already exists, always show connection dialog for a fresh tab

src/PlanViewer.App/Controls/QueryStoreGridControl.axaml.cs

@@ -93,6 +93,16 @@ public QueryStoreGridControl(ServerConnection serverConnection, ICredentialServi
         }, Avalonia.Threading.DispatcherPriority.Loaded);
     }
 
+    /// <summary>
+    /// Sets the initial slicer time range (e.g. from overview drill-down).
+    /// Must be called before the control is loaded to take effect on the first fetch.
+    /// </summary>
+    public void SetInitialTimeRange(DateTime startUtc, DateTime endUtc)
+    {
+        _slicerStartUtc = startUtc;
+        _slicerEndUtc = endUtc;
+    }
+
     private void PopulateDatabaseBox(List<string> databases, string selectedDatabase)
     {
         QsDatabaseBox.ItemsSource = databases;

src/PlanViewer.App/Controls/QueryStoreOverviewControl.axaml

@@ -0,0 +1,62 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:controls="using:PlanViewer.App.Controls"
+             x:Class="PlanViewer.App.Controls.QueryStoreOverviewControl">
+    <Grid x:Name="RootGrid" Background="{DynamicResource BackgroundBrush}">
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="1*"/>
+            <RowDefinition Height="2*"/>
+            <RowDefinition Height="2*"/>
+        </Grid.RowDefinitions>
+
+        <!-- Row 0: Progress bar (always visible to reserve space, toggle IsIndeterminate) -->
+        <ProgressBar x:Name="LoadingBar" Grid.Row="0" IsIndeterminate="False"
+                     Height="3" Margin="0"
+                     Foreground="{DynamicResource AccentBrush}"/>
+
+        <!-- Row 1: Donut + TimeSlicer + WaitStats -->
+        <Grid Grid.Row="1" Margin="10">
+            <Grid.ColumnDefinitions>
+                <ColumnDefinition Width="0.6*"/>
+                <ColumnDefinition Width="2*"/>
+                <ColumnDefinition Width="2*"/>
+            </Grid.ColumnDefinitions>
+
+            <!-- Donut chart area -->
+            <Border Grid.Column="0" Background="{DynamicResource BackgroundLightBrush}"
+                    CornerRadius="4" Margin="0,0,5,0" ClipToBounds="True">
+                <Grid RowDefinitions="Auto,*">
+                    <TextBlock Grid.Row="0" Text="QS States" FontSize="11" FontWeight="SemiBold"
+                               Foreground="{DynamicResource ForegroundBrush}"
+                               HorizontalAlignment="Center" Margin="0,4,0,0"/>
+                    <Canvas x:Name="DonutCanvas" Grid.Row="1"/>
+                </Grid>
+            </Border>
+
+            <!-- Time slicer (consolidated) - reuses the full TimeRangeSlicerControl -->
+            <controls:TimeRangeSlicerControl x:Name="OverviewTimeSlicer"
+                                              Grid.Column="1" Margin="5,0,5,0"
+                                              VerticalAlignment="Stretch"/>
+
+            <!-- Wait stats ribbon (consolidated by database) -->
+            <Border Grid.Column="2" Background="{DynamicResource BackgroundLightBrush}"
+                    CornerRadius="4" Margin="5,0,0,0" ClipToBounds="True">
+                <Grid RowDefinitions="Auto,*">
+                    <TextBlock Grid.Row="0" Text="Wait Stats by Database" FontSize="11" FontWeight="SemiBold"
+                               Foreground="{DynamicResource ForegroundBrush}"
+                               HorizontalAlignment="Center" Margin="0,4,0,0"/>
+                    <Border x:Name="WaitStatsBorder" Grid.Row="1" ClipToBounds="True">
+                        <Canvas x:Name="WaitStatsCanvas" Background="Transparent"/>
+                    </Border>
+                </Grid>
+            </Border>
+        </Grid>
+
+        <!-- Row 1: Total metrics bar cards -->
+        <Grid x:Name="TotalMetricsGrid" Grid.Row="2" Margin="10"/>
+
+        <!-- Row 2: Avg metrics bar cards -->
+        <Grid x:Name="AvgMetricsGrid" Grid.Row="3" Margin="10"/>
+    </Grid>
+</UserControl>