feat(merge): toggle add/remove per side, MAIN/INCOMING labels, files readout

- Conflict accept is now a per-side toggle: > adds MAIN (ours), < adds INCOMING
  (theirs) in click order (first on top); clicking again removes that side, so each
  side is included at most once. Region content is rebuilt from the included set.
- Drop the separate reset (x) control — toggling both off clears the region.
- Relabel the panes/tooltips Ours/Theirs -> MAIN/INCOMING (merge target vs task).
- Add a cross-file 'N of M files unresolved' readout (FilesSummary) so you can see
  how many more files still have conflicts. en/de updated; Ui 128 + Loc 16 green.

src/ClaudeDo.Ui/Views/Conflicts/ConflictResolverView.axaml

@@ -104,7 +104,7 @@
       </Border>
 
       <!-- Toolbar: change nav · file switcher · readout -->
-      <Grid Grid.Row="2" ColumnDefinitions="Auto,Auto,Auto,*,Auto" Margin="0,0,0,8"
+      <Grid Grid.Row="2" ColumnDefinitions="Auto,Auto,Auto,*,Auto,Auto" Margin="0,0,0,8"
             IsVisible="{Binding HasCurrent}">
         <Button Grid.Column="0" Classes="btn" Content="↑" Margin="0,0,4,0" Padding="10,4"
                 ToolTip.Tip="{loc:Tr conflictResolver.prevConflict}"
@@ -121,7 +121,11 @@
             </DataTemplate>
           </ComboBox.ItemTemplate>
         </ComboBox>
-        <TextBlock Grid.Column="4" Classes="meta" VerticalAlignment="Center"
+        <TextBlock Grid.Column="4" Classes="meta" VerticalAlignment="Center" Margin="0,0,14,0"
+                   Foreground="{DynamicResource AmberBrush}"
+                   IsVisible="{Binding HasMultipleFiles}"
+                   Text="{Binding FilesSummary}"/>
+        <TextBlock Grid.Column="5" Classes="meta" VerticalAlignment="Center"
                    Foreground="{DynamicResource TextDimBrush}"
                    Text="{Binding PositionText}"/>
       </Grid>