Fix: mic meter invisible after footer grid column removal

When the Socials button moved to the preview row, its 220px first column
was removed from the footer grid. The mic meter StackPanel still referenced
Grid.Column=1 which no longer exists — moved to Grid.Column=0. Build 0w.

MainWindow.xaml

@@ -1387,8 +1387,7 @@
                     <RowDefinition Height="Auto"/>
                 </Grid.RowDefinitions>
 
-                <!-- Line 1: Social controls on the LEFT (under scenes/sources),
-                     sound meter + volume control CENTERED beneath the preview panel.
+                <!-- Line 1: Mic meter + volume control CENTERED beneath the preview panel.
                      Audio is KISS: desktop/game audio is automatic (WASAPI loopback);
                      the mic meter is the creator's only footer audio control (the
                      game audio bar lives INSIDE the preview window, overlaid at its
@@ -1397,11 +1396,10 @@
                 <Grid Grid.Row="0">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="*"/>
-                        <ColumnDefinition Width="300"/>
                     </Grid.ColumnDefinitions>
 
                     <!-- Mic meter + volume: centered under the preview panel -->
-                    <StackPanel Grid.Column="1" Orientation="Horizontal"
+                    <StackPanel Grid.Column="0" Orientation="Horizontal"
                                 HorizontalAlignment="Center" VerticalAlignment="Center">
                     <Button Command="{Binding OpenMicPickerCommand}"
                             Style="{StaticResource YtButtonSecondary}" Padding="12,4"