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>

lib/main.dart

@@ -5,6 +5,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:pdfrx/pdfrx.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import 'editor/pdf/pen_capture_region.dart';
 import 'editor/persistence/sidecar_flush_observer.dart';
 import 'theme/app_theme.dart';
 import 'diagnostics/badnote_log.dart';
@@ -18,7 +19,9 @@ import 'services/webdav_sync_service.dart';
 import 'storage/sqlite_to_sidecar_migrator.dart';
 
 Future<void> main() async {
-  WidgetsFlutterBinding.ensureInitialized();
+  // Kind-gated PDF pen capture MUST install before runApp — without it
+  // PenCaptureRegion.currentPointerKind stays null and stylus ink never hits.
+  PenCaptureBinding.ensureInitialized();
   // pdfrx native engine init (required before any PdfViewer is built).
   pdfrxFlutterInitialize();