feat(usage): split throttle thresholds per bucket, add draggable gauge markers

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -570,7 +570,9 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
         {
             var vm = _usageMonitorVmFactory();
             vm.ErrorReported += FlashFooterError;
-            await vm.LoadAsync();
+            // Show first, load after: the initial transcript scan takes seconds, and awaiting it
+            // here left the pill looking unresponsive until the window finally appeared.
+            vm.BeginLoad();
             await Dialogs.ShowUsageMonitorAsync(vm);
         }
         finally { _usageMonitorOpen = false; }