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.

src/ClaudeDo.Ui/ViewModels/Islands/DetailsIslandViewModel.cs

@@ -1129,9 +1129,13 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
     private async System.Threading.Tasks.Task StopAsync()
     {
         if (Task == null || !IsRunning) return;
-        if (!_worker.IsConnected) return;
+        if (!_worker.IsConnected)
+        {
+            ErrorReported?.Invoke(Loc.T("vm.detailsIsland.stopOffline"));
+            return;
+        }
         try { await _worker.CancelTaskAsync(Task.Id); }
-        catch { /* offline */ }
+        catch (Exception ex) { ErrorReported?.Invoke(Loc.T("vm.detailsIsland.stopFailed", ex.Message)); }
     }
 
     [RelayCommand(CanExecute = nameof(CanEnqueue))]
@@ -1144,7 +1148,7 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
             AgentState = "queued";
             ReportBaseDirty(baseDirty);
         }
-        catch { /* offline */ }
+        catch (Exception ex) { ErrorReported?.Invoke(Loc.T("vm.detailsIsland.enqueueFailed", ex.Message)); }
     }
 
     private void ReportBaseDirty(BaseDirtyWarningDto? warning)
@@ -1167,7 +1171,7 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
             await _worker.SetTaskStatusAsync(Task.Id, ClaudeDo.Data.Models.TaskStatus.Idle);
             AgentState = "idle";
         }
-        catch { /* offline */ }
+        catch (Exception ex) { ErrorReported?.Invoke(Loc.T("vm.detailsIsland.dequeueFailed", ex.Message)); }
     }
 
     private bool CanDequeue() =>
@@ -1223,7 +1227,7 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase, IDisposable
             AgentState = "queued";
             ReportBaseDirty(baseDirty);
         }
-        catch { /* offline */ }
+        catch (Exception ex) { ErrorReported?.Invoke(Loc.T("vm.detailsIsland.resetAndRetryFailed", ex.Message)); }
     }
 
     // Reset & Retry discards the branch/uncommitted work and queues an autonomous run into the