fix: restore PDF pen capture and overhaul sticky/pens/pages

Reinstall PenCaptureBinding so stylus ink hits again; keep finger Listener translucent under pinch; page-anchor sticky with drag/resize; OneNote pen slots (brush+width+color); blank-note multi-page; default side button to hold-select-text.

Co-authored-by: Cursor <cursoragent@cursor.com>

test/sidecar_repository_test.dart

@@ -122,6 +122,26 @@ void main() {
     reopened.dispose();
   });
 
+  test('schedulePageCountSave persists and restores pageCount', () async {
+    final repo = await SidecarRepository.open(src, debounce: _fast);
+    repo.schedulePageCountSave(5);
+    await repo.flush();
+    expect(repo.sidecar.pageCount, 5);
+    repo.dispose();
+
+    final reopened = await SidecarRepository.open(src, debounce: _fast);
+    expect(reopened.sidecar.pageCount, 5);
+    reopened.dispose();
+  });
+
+  test('notebook open normalizes missing pageCount to 1', () async {
+    final noteSrc = '${tmpDir.path}/notebook';
+    final repo =
+        await SidecarRepository.open(noteSrc, docType: 'notebook', debounce: _fast);
+    expect(repo.sidecar.pageCount, 1);
+    repo.dispose();
+  });
+
   test('removing a highlight persists (un-highlight)', () async {
     final repo = await SidecarRepository.open(src, debounce: _fast);
     repo.scheduleHighlightSave(0, const [