feat(ui): add OperationStatus feedback primitive and OperationIndicator control

Foundation for long-running-operation feedback (P0-1). OperationStatus tracks
IsRunning/ShowIndicator(300ms grace)/Elapsed/IsStalled(60s since last Report)
via an injectable TimeProvider, no static timer. OperationIndicator binds a
status to the shared spinner style. Pre-provisions ops.* locale keys for
groups A and C; no ViewModel wired up yet.

src/ClaudeDo.Ui/Views/Controls/OperationIndicator.axaml.cs

@@ -0,0 +1,26 @@
+using Avalonia;
+using Avalonia.Controls;
+using ClaudeDo.Ui.Services;
+
+namespace ClaudeDo.Ui.Views.Controls;
+
+public partial class OperationIndicator : UserControl
+{
+    public static readonly StyledProperty<OperationStatus?> StatusProperty =
+        AvaloniaProperty.Register<OperationIndicator, OperationStatus?>(nameof(Status));
+
+    public OperationStatus? Status
+    {
+        get => GetValue(StatusProperty);
+        set => SetValue(StatusProperty, value);
+    }
+
+    public OperationIndicator() => InitializeComponent();
+
+    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+    {
+        base.OnPropertyChanged(change);
+        if (change.Property == StatusProperty)
+            DataContext = change.GetNewValue<OperationStatus?>();
+    }
+}