fix(ui): stop the reconcile tick on native close, index rows in the tick

Two follow-ups to the Phase 3 reconcile tick:

- LogVisualizer and WorktreesOverview only stopped their timer in the Close
  command, but ShowLogVisualizerAsync/ShowWorktreesOverviewAsync had no
  dlg.Closed fallback (unlike the MergeHelper picker). An Alt+F4 or owner
  close left a 4s timer polling the worker / re-running LoadAsync on an
  orphaned VM, accumulating one per open. Extracted StopReconcileTick on both
  VMs and wired it from Closed.
- The tick scanned Items linearly per id; at the 500-row cap that is ~250k
  string comparisons every few seconds. Index the rows once instead.

src/ClaudeDo.Ui/ViewModels/Modals/LogVisualizerViewModel.cs

@@ -75,10 +75,18 @@ public sealed partial class LogVisualizerViewModel : ViewModelBase
 
     [RelayCommand]
     private void Close()
+    {
+        StopReconcileTick();
+        CloseAction?.Invoke();
+    }
+
+    /// <summary>Stops the reconcile tick. Also called from the dialog's native-close fallback
+    /// (WindowDialogService), which bypasses <see cref="CloseCommand"/> — otherwise an Alt+F4
+    /// leaves the timer polling the worker on an orphaned VM. Idempotent.</summary>
+    internal void StopReconcileTick()
     {
         _reconcileTimer.Stop();
         _reconcileTimer.Dispose();
-        CloseAction?.Invoke();
     }
 
     private bool CanCopyLast() => Rows.Count > 0;

src/ClaudeDo.Ui/ViewModels/Modals/WorktreesOverviewModalViewModel.cs

@@ -192,10 +192,18 @@ public sealed partial class WorktreesOverviewModalViewModel : ViewModelBase
 
     [RelayCommand]
     private void Close()
+    {
+        StopReconcileTick();
+        CloseAction?.Invoke();
+    }
+
+    /// <summary>Stops the reconcile tick. Also called from the dialog's native-close fallback
+    /// (WindowDialogService), which bypasses <see cref="CloseCommand"/> — otherwise an Alt+F4
+    /// leaves the timer re-running LoadAsync (git + DB) on an orphaned VM. Idempotent.</summary>
+    internal void StopReconcileTick()
     {
         _reconcileTimer.Stop();
         _reconcileTimer.Dispose();
-        CloseAction?.Invoke();
     }
 
     [RelayCommand]