refactor(ui): remove unused Sort button from MyDay header

It was a no-op placeholder command; removed the button, command,
locale keys, and now-unused Icon.Sort geometry.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Ui/Views/Islands/TasksIslandView.axaml

@@ -28,9 +28,6 @@
                   IsVisible="{Binding HasStatusPill}">
             <TextBlock Text="{Binding StatusPill}"/>
           </Border>
-          <Button Classes="icon-btn" Command="{Binding SortCommand}" ToolTip.Tip="{loc:Tr tasks.sortTip}">
-            <PathIcon Width="15" Height="15" Data="{StaticResource Icon.Sort}"/>
-          </Button>
           <Button Classes="icon-btn" Classes.active="{Binding IsShowingCompleted}"
                   Command="{Binding ToggleShowCompletedCommand}"
                   ToolTip.Tip="{loc:Tr tasks.showCompletedTip}">