feat(mission-control): column picker for the overview grid

Auto keeps the pane-count heuristic; 1-4 fixes the column count (capped at
the pane count). Persisted to ui.config.json as MissionControlColumns.

src/ClaudeDo.Ui/AppSettings.cs

@@ -16,6 +16,9 @@ public sealed class AppSettings
     public string DiffViewMode { get; set; } = "unified";
     public bool DiffWrapLines { get; set; }
 
+    /// <summary>Mission Control overview column count; 0 = auto (derived from the pane count).</summary>
+    public int MissionControlColumns { get; set; }
+
     private static readonly string DefaultConfigPath = Paths.Expand("~/.claudeDo/ui.config.json");
 
     /// Where this instance persists. Instance-level (not static) so tests can redirect it —

src/ClaudeDo.Ui/Converters/SimpleConverters.cs

@@ -19,6 +19,14 @@ public sealed class HexBrushConverter : OneWayConverter
             : Avalonia.Application.Current?.TryGetResource(parameter as string ?? "", null, out var res) == true ? res : null;
 }
 
+/// <summary>True when the value's string form equals the parameter (segmented-switch active state).</summary>
+public sealed class EqualsParameterConverter : OneWayConverter
+{
+    public static EqualsParameterConverter Instance { get; } = new();
+    public override object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => Equals(value?.ToString(), parameter as string);
+}
+
 public sealed class UpperCaseConverter : OneWayConverter
 {
     public static UpperCaseConverter Instance { get; } = new();

src/ClaudeDo.Ui/ViewModels/MissionControlViewModel.cs

@@ -18,6 +18,7 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
 {
     private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
     private readonly IWorkerClient _worker;
+    private readonly AppSettings? _settings;
     private readonly Action<string, string, DateTime> _onTaskStarted;
     private readonly Action<string, string, string, DateTime> _onTaskFinished;
     private readonly Action<string> _onTaskUpdated;
@@ -44,6 +45,9 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
 
     [ObservableProperty] private int _columnCount = 1;
 
+    /// <summary>User-picked column count for the overview grid; 0 = auto (derived from the pane count).</summary>
+    [ObservableProperty] private int _columnPreference;
+
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(LayoutToggleLabel))]
     private bool _isFocusMode;
@@ -94,11 +98,13 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
 
     public UsagePillViewModel UsagePill { get; }
 
-    public MissionControlViewModel(IDbContextFactory<ClaudeDoDbContext> dbFactory, IWorkerClient worker, UsagePillViewModel usagePill)
+    public MissionControlViewModel(IDbContextFactory<ClaudeDoDbContext> dbFactory, IWorkerClient worker, UsagePillViewModel usagePill, AppSettings? settings = null)
     {
         _dbFactory = dbFactory;
         _worker = worker;
         UsagePill = usagePill;
+        _settings = settings;
+        _columnPreference = Math.Clamp(settings?.MissionControlColumns ?? 0, 0, MaxColumns);
 
         ConPtySessions.CollectionChanged += OnConPtySessionsChanged;
         Panes.CollectionChanged += OnPanesChanged;
@@ -334,6 +340,32 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
     [RelayCommand]
     private void ToggleLayout() => IsFocusMode = !IsFocusMode;
 
+    /// <summary>Upper bound of the column picker.</summary>
+    public const int MaxColumns = 4;
+
+    /// <summary>Sets the column preference from the header picker ("0" = auto) and persists it.</summary>
+    [RelayCommand]
+    private void SetColumns(string value) => ColumnPreference = Math.Clamp(int.Parse(value), 0, MaxColumns);
+
+    partial void OnColumnPreferenceChanged(int value)
+    {
+        UpdateColumnCount();
+        if (_settings is null) return;
+        _settings.MissionControlColumns = value;
+        try { _settings.Save(); }
+        catch (Exception ex) { ErrorReported?.Invoke(ex.Message); }
+    }
+
+    // Never more columns than panes, so a wide preference doesn't leave empty cells.
+    private void UpdateColumnCount() => ColumnCount = ColumnPreference > 0
+        ? Math.Max(1, Math.Min(ColumnPreference, Panes.Count))
+        : Panes.Count switch
+        {
+            <= 1 => 1,
+            <= 4 => 2,
+            _    => 3,
+        };
+
     // Fetches the launch spec for a task's worktree and hosts an embedded ConPTY session as a
     // Command Center pane (task-based only).
     public async System.Threading.Tasks.Task OpenConPtySessionAsync(string taskId)
@@ -716,12 +748,7 @@ public sealed partial class MissionControlViewModel : ViewModelBase, IDisposable
 
     private void OnPanesChanged(object? sender, NotifyCollectionChangedEventArgs e)
     {
-        ColumnCount = Panes.Count switch
-        {
-            <= 1 => 1,
-            <= 4 => 2,
-            _    => 3,
-        };
+        UpdateColumnCount();
         OnPropertyChanged(nameof(HasPanes));
         if (e.Action == NotifyCollectionChangedAction.Add && e.NewItems?[0] is ConPtyPaneViewModel added)
             FocusedPane = added;

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

@@ -102,6 +102,27 @@
               </Flyout>
             </Button.Flyout>
           </Button>
+          <Border Classes="segmented" VerticalAlignment="Center"
+                  IsVisible="{Binding !IsFocusMode}"
+                  ToolTip.Tip="{loc:Tr missionControl.columns}">
+            <StackPanel Orientation="Horizontal">
+              <Button Classes="segment" Content="{loc:Tr missionControl.columnsAuto}"
+                      Classes.active="{Binding ColumnPreference, Converter={x:Static conv:EqualsParameterConverter.Instance}, ConverterParameter=0}"
+                      Command="{Binding SetColumnsCommand}" CommandParameter="0"/>
+              <Button Classes="segment" Content="1"
+                      Classes.active="{Binding ColumnPreference, Converter={x:Static conv:EqualsParameterConverter.Instance}, ConverterParameter=1}"
+                      Command="{Binding SetColumnsCommand}" CommandParameter="1"/>
+              <Button Classes="segment" Content="2"
+                      Classes.active="{Binding ColumnPreference, Converter={x:Static conv:EqualsParameterConverter.Instance}, ConverterParameter=2}"
+                      Command="{Binding SetColumnsCommand}" CommandParameter="2"/>
+              <Button Classes="segment" Content="3"
+                      Classes.active="{Binding ColumnPreference, Converter={x:Static conv:EqualsParameterConverter.Instance}, ConverterParameter=3}"
+                      Command="{Binding SetColumnsCommand}" CommandParameter="3"/>
+              <Button Classes="segment" Content="4"
+                      Classes.active="{Binding ColumnPreference, Converter={x:Static conv:EqualsParameterConverter.Instance}, ConverterParameter=4}"
+                      Command="{Binding SetColumnsCommand}" CommandParameter="4"/>
+            </StackPanel>
+          </Border>
           <Button Classes="icon-btn"
                   Command="{Binding ToggleLayoutCommand}"
                   ToolTip.Tip="{Binding LayoutToggleLabel}">