send the map selection to change detection and show the modified class

The comparison hook runs before the selection state is declared in App, so the
selection is read through a getter at the moment the run starts rather than
captured at render. The panel gains the modified count, which until now was
folded into removed plus added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/components/analysis/ChangeDetectionPanel.tsx

@@ -120,6 +120,10 @@ export function ChangeDetectionPanel({
               <span className="metric">{result.removed_count}</span>
               <span>Verdwenen</span>
             </div>
+            <div>
+              <span className="metric">{result.modified_count ?? 0}</span>
+              <span>Gewijzigd</span>
+            </div>
             <div>
               <span className="metric">{result.unchanged_count}</span>
               <span>Ongewijzigd</span>