feat(mission-control): make overview panes and queue strip individually resizable

Replace the UniformGrid (all tiles forced to equal size) with a real
Grid + GridSplitters built in code-behind per pane count/column count,
so panes resize individually. The queue strip's fixed 210px column
becomes a drag-resizable Grid column (min 160px) that collapses to 0
when nothing is queued, replacing the old dock-based fixed width.

src/ClaudeDo.Ui/Views/MissionControl/MissionControlView.axaml.cs

@@ -1,5 +1,10 @@
+using System;
+using System.Collections.Specialized;
+using System.ComponentModel;
 using Avalonia.Controls;
 using Avalonia.Interactivity;
+using Avalonia.Layout;
+using Avalonia.Media;
 using Avalonia.Platform.Storage;
 using ClaudeDo.Ui.ViewModels;
 
@@ -7,9 +12,20 @@ namespace ClaudeDo.Ui.Views.MissionControl;
 
 public partial class MissionControlView : UserControl
 {
+    private const double SplitterSize = 6;
+    private const double DefaultQueueWidth = 210;
+    private const double MinQueueWidth = 160;
+    private const double MinPaneWidth = 220;
+    private const double MinPaneHeight = 140;
+
+    private MissionControlViewModel? _vm;
+    private GridLength _queueWidth = new(DefaultQueueWidth, GridUnitType.Pixel);
+
     public MissionControlView()
     {
         InitializeComponent();
+        DataContextChanged += OnDataContextChanged;
+        QueueSplitter.DragCompleted += (_, _) => _queueWidth = BodyGrid.ColumnDefinitions[2].Width;
     }
 
     // Ad-hoc ConPTY session: the view owns the folder picker, the VM only takes the chosen path.
@@ -28,4 +44,127 @@ public partial class MissionControlView : UserControl
 
         await vm.OpenAdHocConPtySessionAsync(folders[0].Path.LocalPath);
     }
+
+    private void OnDataContextChanged(object? sender, EventArgs e)
+    {
+        if (_vm is not null)
+        {
+            _vm.Panes.CollectionChanged -= OnPanesChanged;
+            _vm.PropertyChanged -= OnViewModelPropertyChanged;
+        }
+
+        _vm = DataContext as MissionControlViewModel;
+
+        if (_vm is not null)
+        {
+            _vm.Panes.CollectionChanged += OnPanesChanged;
+            _vm.PropertyChanged += OnViewModelPropertyChanged;
+        }
+
+        RebuildOverviewGrid();
+        UpdateQueueColumn();
+    }
+
+    private void OnPanesChanged(object? sender, NotifyCollectionChangedEventArgs e) => RebuildOverviewGrid();
+
+    private void OnViewModelPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName == nameof(MissionControlViewModel.ColumnCount))
+            RebuildOverviewGrid();
+        else if (e.PropertyName == nameof(MissionControlViewModel.HasQueued))
+            UpdateQueueColumn();
+    }
+
+    // The queue column is Pixel-widthed (so the splitter can drag it) — when nothing is
+    // queued it collapses to 0 instead of leaving a blank gap, and remembers the last
+    // dragged width for the rest of this window's lifetime (not persisted beyond it).
+    private void UpdateQueueColumn()
+    {
+        var queueColumn = BodyGrid.ColumnDefinitions[2];
+        if (_vm?.HasQueued == true)
+        {
+            queueColumn.MinWidth = MinQueueWidth;
+            queueColumn.Width = _queueWidth;
+        }
+        else
+        {
+            queueColumn.MinWidth = 0;
+            queueColumn.Width = new GridLength(0, GridUnitType.Pixel);
+        }
+    }
+
+    // Replaces the old UniformGrid with a real Grid + GridSplitters so panes resize
+    // individually. Column splitters span every row (resize that whole column vs. its
+    // neighbor); row splitters span every column. Rebuilt from scratch whenever the pane
+    // count or column count changes — per-pane sizes are intentionally not preserved across
+    // a rebuild (session-only resizing, reset to the default split when panes come/go).
+    private void RebuildOverviewGrid()
+    {
+        OverviewGrid.Children.Clear();
+        OverviewGrid.ColumnDefinitions.Clear();
+        OverviewGrid.RowDefinitions.Clear();
+
+        var panes = _vm?.Panes;
+        if (panes is not { Count: > 0 }) return;
+
+        var columns = Math.Max(1, _vm!.ColumnCount);
+        var rows = (int)Math.Ceiling(panes.Count / (double)columns);
+
+        for (var c = 0; c < columns; c++)
+        {
+            if (c > 0) OverviewGrid.ColumnDefinitions.Add(new ColumnDefinition(GridLength.Auto));
+            OverviewGrid.ColumnDefinitions.Add(new ColumnDefinition(new GridLength(1, GridUnitType.Star)) { MinWidth = MinPaneWidth });
+        }
+
+        for (var r = 0; r < rows; r++)
+        {
+            if (r > 0) OverviewGrid.RowDefinitions.Add(new RowDefinition(GridLength.Auto));
+            OverviewGrid.RowDefinitions.Add(new RowDefinition(new GridLength(1, GridUnitType.Star)) { MinHeight = MinPaneHeight });
+        }
+
+        var totalGridRows = rows * 2 - 1;
+        var totalGridCols = columns * 2 - 1;
+
+        for (var c = 1; c < columns; c++)
+        {
+            var splitter = new GridSplitter
+            {
+                Width = SplitterSize,
+                Background = Brushes.Transparent,
+                HorizontalAlignment = HorizontalAlignment.Stretch,
+                VerticalAlignment = VerticalAlignment.Stretch,
+                ResizeDirection = GridResizeDirection.Columns,
+                ResizeBehavior = GridResizeBehavior.PreviousAndNext,
+            };
+            Grid.SetColumn(splitter, c * 2 - 1);
+            Grid.SetRow(splitter, 0);
+            Grid.SetRowSpan(splitter, totalGridRows);
+            OverviewGrid.Children.Add(splitter);
+        }
+
+        for (var r = 1; r < rows; r++)
+        {
+            var splitter = new GridSplitter
+            {
+                Height = SplitterSize,
+                Background = Brushes.Transparent,
+                HorizontalAlignment = HorizontalAlignment.Stretch,
+                VerticalAlignment = VerticalAlignment.Stretch,
+                ResizeDirection = GridResizeDirection.Rows,
+                ResizeBehavior = GridResizeBehavior.PreviousAndNext,
+            };
+            Grid.SetColumn(splitter, 0);
+            Grid.SetColumnSpan(splitter, totalGridCols);
+            Grid.SetRow(splitter, r * 2 - 1);
+            OverviewGrid.Children.Add(splitter);
+        }
+
+        for (var i = 0; i < panes.Count; i++)
+        {
+            var presenter = new ContentControl { Content = panes[i] };
+            Grid.SetColumn(presenter, (i % columns) * 2);
+            Grid.SetRow(presenter, (i / columns) * 2);
+            OverviewGrid.Children.Add(presenter);
+        }
+    }
 }