feat(ui): separate OperationStatus per worktree action (refresh/cleanup/reset/force-remove/batch-merge)

Replaces the shared IsBusy/IsMerging flags in WorktreesOverviewModalViewModel and the
reset flow in WorktreesSettingsTabViewModel with dedicated OperationStatus instances
shown via OperationIndicator, so a running Refresh no longer blocks the Cleanup
indicator. ForceRemove gains a CanExecute guard against re-entrancy while it's running,
and the reconcile tick's busy guard now checks all four action statuses instead of the
old IsBusy||IsMerging pair.

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

@@ -47,7 +47,7 @@ public class WorktreesSettingsTabViewModelTests
         await vm.ConfirmResetAllCommand.ExecuteAsync(null);
 
         Assert.Contains(worker.ExceptionMessage, vm.StatusMessage);
-        Assert.False(vm.IsBusy);
+        Assert.False(vm.ResetStatus.IsRunning);
         Assert.False(vm.ShowResetConfirm);
     }
 }