[CmdPal] Better support for long labels in empty content and commandbar (#38974)

Closes: #38970

Before:
<img width="605" alt="image" src="https://github.com/user-attachments/assets/8310e08f-c471-4663-9000-bfd1eb8c99f3" />

After:
<img width="514" alt="image" src="https://github.com/user-attachments/assets/b1e4c5f6-cd6b-42b2-9a23-3e1e3642202a" />

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/CommandBar.xaml

@@ -71,9 +71,9 @@
         Padding="4"
         ColumnSpacing="8">
         <Grid.ColumnDefinitions>
-            <ColumnDefinition Width="Auto" />
             <ColumnDefinition Width="Auto" />
             <ColumnDefinition Width="*" />
+            <ColumnDefinition Width="Auto" />
         </Grid.ColumnDefinitions>
 
         <Grid
@@ -133,6 +133,8 @@
             VerticalAlignment="Center"
             Style="{StaticResource CaptionTextBlockStyle}"
             Text="{x:Bind CurrentPageViewModel.Title, Mode=OneWay}"
+            TextTrimming="CharacterEllipsis"
+            TextWrapping="NoWrap"
             Visibility="{x:Bind CurrentPageViewModel.IsNested, Mode=OneWay}" />
         <StackPanel
             Grid.Column="2"