feat(claude-do): [A4] WeeklyReport, DailyPrep und Planning-Aktionen auf OperationStatus umstellen

WeeklyReportModalViewModel.Generate, PrepPanelViewModel.PlanDayAsync und die beiden
Planning-Aktionen (QueuePlanningSubtasksAsync, FinalizePlanningSessionAsync) laufen jetzt
durch je eine OperationStatus + OperationIndicator statt handgebauter Spinner. Die beiden
Planning-Aktionen teilen sich eine Instanz, angezeigt im Tasks-Island-Header, weil sie aus
einem sofort schliessenden Kontextmenue ausgeloest werden und es keine dauerhafte
Pro-Zeilen-Flaeche gibt, an die ein Indikator gehaengt werden koennte.

tests/ClaudeDo.Ui.Tests/ViewModels/PrepPanelViewModelTests.cs

@@ -0,0 +1,61 @@
+using ClaudeDo.Ui.ViewModels.Islands;
+
+namespace ClaudeDo.Ui.Tests.ViewModels;
+
+public class PrepPanelViewModelTests
+{
+    private sealed class Worker : StubWorkerClient
+    {
+        public TaskCompletionSource<bool> Gate { get; } = new();
+        public bool Throw { get; set; }
+
+        public override Task<bool> RunDailyPrepNowAsync() =>
+            Throw ? Task.FromException<bool>(new InvalidOperationException("boom")) : Gate.Task;
+    }
+
+    [Fact]
+    public async Task PlanDay_sets_PrepOperation_IsRunning_before_the_started_broadcast_arrives()
+    {
+        var worker = new Worker();
+        var vm = new PrepPanelViewModel(worker);
+
+        var plan = vm.PlanDayCommand.ExecuteAsync(null);
+
+        Assert.True(vm.PrepOperation.IsRunning);
+        Assert.False(vm.IsPrepRunning); // the broadcast hasn't fired yet
+
+        worker.Gate.SetResult(true);
+        await plan;
+
+        Assert.False(vm.PrepOperation.IsRunning);
+    }
+
+    [Fact]
+    public async Task PlanDayCommand_CanExecute_is_locked_while_running()
+    {
+        var worker = new Worker();
+        var vm = new PrepPanelViewModel(worker);
+
+        var plan = vm.PlanDayCommand.ExecuteAsync(null);
+        Assert.False(vm.PlanDayCommand.CanExecute(null));
+        Assert.False(vm.IsPlanDayEnabled);
+
+        worker.Gate.SetResult(true);
+        await plan;
+
+        Assert.True(vm.PlanDayCommand.CanExecute(null));
+        Assert.True(vm.IsPlanDayEnabled);
+    }
+
+    [Fact]
+    public async Task PlanDay_ends_the_operation_when_the_worker_call_throws()
+    {
+        var worker = new Worker { Throw = true };
+        var vm = new PrepPanelViewModel(worker);
+
+        await vm.PlanDayCommand.ExecuteAsync(null);
+
+        Assert.False(vm.PrepOperation.IsRunning);
+        Assert.True(vm.PlanDayCommand.CanExecute(null));
+    }
+}