fix(ui): silent no-ops raise ErrorReported instead of swallowing failures (UX-Audit #1)

Stop/Enqueue/Dequeue/Reset&Retry (DetailsIslandViewModel), status/cancel/reject
commands (TasksIslandViewModel), Mission Control's drag-enqueue and queue
refresh, and "Open findings folder" (ListsIslandViewModel) used to catch {}
or silently return on a blocked precondition. They now report through the
existing ErrorReported -> FlashFooterError path, with new en/de locale keys
and Ui.Tests covering each converted command.

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

@@ -278,14 +278,40 @@ public class MissionControlViewModelTests : IDisposable
         using var vm = BuildVm(worker);
         await vm.OpenConPtySessionAsync("t1");
 
+        string? error = null;
+        vm.ErrorReported += msg => error = msg;
+
         await vm.EnqueueTaskAsync("t1");
 
         Assert.Empty(worker.QueuedTaskIds);
+        Assert.NotNull(error);
         await using var verify = NewContext();
         var entity = await verify.Tasks.FirstAsync(t => t.Id == "t1");
         Assert.Equal(TaskStatus.Idle, entity.Status);
     }
 
+    private sealed class ThrowingSetStatusWorkerClient : StubWorkerClient
+    {
+        public Exception Error { get; init; } = new Exception("enqueue offline");
+        public override Task<BaseDirtyWarningDto?> SetTaskStatusAsync(string taskId, TaskStatus status) =>
+            throw Error;
+    }
+
+    [Fact]
+    public async Task EnqueueTaskAsync_WhenWorkerThrows_RaisesErrorReported()
+    {
+        var worker = new ThrowingSetStatusWorkerClient();
+        using var vm = BuildVm(worker);
+
+        string? error = null;
+        vm.ErrorReported += msg => error = msg;
+
+        await vm.EnqueueTaskAsync("t1");
+
+        Assert.NotNull(error);
+        Assert.Contains("enqueue offline", error);
+    }
+
     private sealed class ThrowingLaunchSpecWorker : StubWorkerClient
     {
         public override Task<LaunchSpec> GetInteractiveLaunchSpecAsync(string taskId, CancellationToken ct = default)