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/models/scratch_link.dart

@@ -2,11 +2,8 @@
 //
 // A PDF-anchored scratch link: a sticky-note "tab" placed at a normalized
 // position (nx, ny in [0,1]) on a specific page of a document. Tapping the
-// anchor opens a split view whose right pane is an infinite freehand scratchpad
-// that BELONGS TO THIS ANCHOR (keyed by [id]).
-//
-// Plain immutable value class (no freezed codegen) so it compiles without a
-// build_runner step. Equality is by value so anchors can be diffed in lists.
+// anchor opens an on-page sticky card that BELONGS TO THIS ANCHOR (keyed by
+// [id]). Optional [nw]/[nh] size the expanded card as fractions of the page.
 
 import 'package:flutter/foundation.dart';
 
@@ -18,6 +15,8 @@ class ScratchLink {
     required this.pageIndex,
     required this.nx,
     required this.ny,
+    this.nw = 0.42,
+    this.nh = 0.36,
   });
 
   /// Stable anchor id (uuid). Doubles as the scratchpad storage key so each
@@ -30,18 +29,26 @@ class ScratchLink {
   /// 0-based page the anchor sits on.
   final int pageIndex;
 
-  /// Normalized horizontal position on the page, in [0, 1].
+  /// Normalized horizontal position on the page, in [0, 1] (top-left of card).
   final double nx;
 
-  /// Normalized vertical position on the page, in [0, 1].
+  /// Normalized vertical position on the page, in [0, 1] (top-left of card).
   final double ny;
 
+  /// Expanded card width as a fraction of page width (clamped on write).
+  final double nw;
+
+  /// Expanded card height as a fraction of page height.
+  final double nh;
+
   ScratchLink copyWith({
     String? id,
     String? documentId,
     int? pageIndex,
     double? nx,
     double? ny,
+    double? nw,
+    double? nh,
   }) =>
       ScratchLink(
         id: id ?? this.id,
@@ -49,6 +56,8 @@ class ScratchLink {
         pageIndex: pageIndex ?? this.pageIndex,
         nx: nx ?? this.nx,
         ny: ny ?? this.ny,
+        nw: nw ?? this.nw,
+        nh: nh ?? this.nh,
       );
 
   Map<String, dynamic> toJson() => {
@@ -57,6 +66,8 @@ class ScratchLink {
         'pageIndex': pageIndex,
         'nx': nx,
         'ny': ny,
+        'nw': nw,
+        'nh': nh,
       };
 
   factory ScratchLink.fromJson(Map<String, dynamic> json) => ScratchLink(
@@ -65,6 +76,8 @@ class ScratchLink {
         pageIndex: (json['pageIndex'] as num).toInt(),
         nx: (json['nx'] as num).toDouble(),
         ny: (json['ny'] as num).toDouble(),
+        nw: (json['nw'] as num?)?.toDouble() ?? 0.42,
+        nh: (json['nh'] as num?)?.toDouble() ?? 0.36,
       );
 
   @override
@@ -76,13 +89,15 @@ class ScratchLink {
           documentId == other.documentId &&
           pageIndex == other.pageIndex &&
           nx == other.nx &&
-          ny == other.ny;
+          ny == other.ny &&
+          nw == other.nw &&
+          nh == other.nh;
 
   @override
-  int get hashCode => Object.hash(id, documentId, pageIndex, nx, ny);
+  int get hashCode => Object.hash(id, documentId, pageIndex, nx, ny, nw, nh);
 
   @override
   String toString() =>
       'ScratchLink(id: $id, documentId: $documentId, pageIndex: $pageIndex, '
-      'nx: $nx, ny: $ny)';
+      'nx: $nx, ny: $ny, nw: $nw, nh: $nh)';
 }