feat: enhance PDF thumbnail navigation and selection logic

integration_test/pdf_view_test.dart

@@ -171,6 +171,36 @@ void main() {
     final pagesSidebar = find.byType(PagesSidebar);
     expect(pagesSidebar, findsOneWidget);
 
+    // Helper to read the background color of a thumbnail tile by page label
+    Color? tileBgForPage(int page) {
+      final pageLabel = find.descendant(
+        of: pagesSidebar,
+        matching: find.text('$page'),
+      );
+      if (pageLabel.evaluate().isEmpty) return null; // not visible yet
+      final decoratedAncestors = find.ancestor(
+        of: pageLabel,
+        matching: find.byType(DecoratedBox),
+      );
+      final decoratedBoxes =
+          decoratedAncestors
+              .evaluate()
+              .map((e) => e.widget)
+              .whereType<DecoratedBox>()
+              .toList();
+      for (final d in decoratedBoxes) {
+        final dec = d.decoration;
+        if (dec is BoxDecoration && dec.color != null) {
+          return dec.color;
+        }
+      }
+      return null;
+    }
+
+    final theme = Theme.of(tester.element(pagesSidebar));
+    // Initially, page 1 should be highlighted
+    expect(tileBgForPage(1), theme.colorScheme.primaryContainer);
+
     // Scroll to make page 3 thumbnail visible
     await tester.drag(pagesSidebar, const Offset(0, -300));
     await tester.pumpAndSettle();
@@ -181,6 +211,8 @@ void main() {
     await tester.pumpAndSettle();
 
     expect(container.read(pdfViewModelProvider).currentPage, 3);
+    // After navigation completes, page 3 should be highlighted
+    expect(tileBgForPage(3), theme.colorScheme.primaryContainer);
   });
 
   testWidgets('PDF View: thumbnails scroll and select', (tester) async {

lib/ui/features/pdf/widgets/pages_sidebar.dart

@@ -18,6 +18,8 @@ class ThumbnailsView extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final theme = Theme.of(context);
+    // Access view model to detect mock viewer mode
+    final viewModel = ref.read(pdfViewModelProvider);
 
     return Container(
       color: theme.colorScheme.surface,
@@ -34,16 +36,24 @@ class ThumbnailsView extends ConsumerWidget {
               final isSelected = currentPage == pageNumber;
               return InkWell(
                 onTap: () {
-                  // Update both controller and provider page
-                  controller.goToPage(
-                    pageNumber: pageNumber,
-                    anchor: PdfPageAnchor.top,
-                  );
-                  try {
-                    ref
-                        .read(pdfViewModelProvider.notifier)
-                        .jumpToPage(pageNumber);
-                  } catch (_) {}
+                  // For real viewer: navigate first and wait for onPageChanged
+                  // to update provider when the page is actually reached.
+                  // For mock/unready: update provider immediately to drive scroll.
+                  final isRealViewer = !viewModel.useMockViewer;
+                  if (isRealViewer && controller.isReady) {
+                    controller.goToPage(
+                      pageNumber: pageNumber,
+                      anchor: PdfPageAnchor.top,
+                    );
+                    // Do not set provider here; let onPageChanged handle it
+                  } else {
+                    // In tests or when controller isn't ready, drive state directly
+                    try {
+                      ref
+                          .read(pdfViewModelProvider.notifier)
+                          .jumpToPage(pageNumber);
+                    } catch (_) {}
+                  }
                 },
                 child: DecoratedBox(
                   decoration: BoxDecoration(