feat: OneNote-style notebooks, text fonts, and page navigation

Add notebook.json containers with multi-member pages, fix PDF text
editing (size/bold/drag/double-tap), index SidecarText in search, and
share keyboard page shortcuts plus a PDF scrubber.

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

lib/storage/badnote_sidecar.dart

@@ -121,6 +121,8 @@ class SidecarText {
     required this.text,
     this.fontSize = 0.03,
     this.color = 0xFF000000,
+    this.fontWeight = 400,
+    this.fontFamily,
   });
 
   /// Stable id (uuid) so edits/deletes address a specific box.
@@ -141,6 +143,12 @@ class SidecarText {
   /// ARGB text color.
   final int color;
 
+  /// CSS-like numeric weight (100–900). Default 400 (regular).
+  final int fontWeight;
+
+  /// Optional family name. Null → editor default (IBM Plex Sans).
+  final String? fontFamily;
+
   SidecarText copyWith({
     String? id,
     double? nx,
@@ -148,6 +156,9 @@ class SidecarText {
     String? text,
     double? fontSize,
     int? color,
+    int? fontWeight,
+    String? fontFamily,
+    bool clearFontFamily = false,
   }) =>
       SidecarText(
         id: id ?? this.id,
@@ -156,6 +167,9 @@ class SidecarText {
         text: text ?? this.text,
         fontSize: fontSize ?? this.fontSize,
         color: color ?? this.color,
+        fontWeight: fontWeight ?? this.fontWeight,
+        fontFamily:
+            clearFontFamily ? null : (fontFamily ?? this.fontFamily),
       );
 
   Map<String, dynamic> toJson() => {
@@ -165,6 +179,8 @@ class SidecarText {
         'text': text,
         'fontSize': fontSize,
         'color': color,
+        'fontWeight': fontWeight,
+        if (fontFamily != null) 'fontFamily': fontFamily,
       };
 
   factory SidecarText.fromJson(Map<String, dynamic> json) => SidecarText(
@@ -174,6 +190,8 @@ class SidecarText {
         text: (json['text'] as String?) ?? '',
         fontSize: (json['fontSize'] as num?)?.toDouble() ?? 0.03,
         color: (json['color'] as num?)?.toInt() ?? 0xFF000000,
+        fontWeight: (json['fontWeight'] as num?)?.toInt() ?? 400,
+        fontFamily: json['fontFamily'] as String?,
       );
 
   @override
@@ -186,15 +204,26 @@ class SidecarText {
           ny == other.ny &&
           text == other.text &&
           fontSize == other.fontSize &&
-          color == other.color;
+          color == other.color &&
+          fontWeight == other.fontWeight &&
+          fontFamily == other.fontFamily;
 
   @override
-  int get hashCode => Object.hash(id, nx, ny, text, fontSize, color);
+  int get hashCode => Object.hash(
+        id,
+        nx,
+        ny,
+        text,
+        fontSize,
+        color,
+        fontWeight,
+        fontFamily,
+      );
 
   @override
   String toString() =>
       'SidecarText(id: $id, nx: $nx, ny: $ny, text: $text, '
-      'fontSize: $fontSize, color: $color)';
+      'fontSize: $fontSize, weight: $fontWeight, family: $fontFamily)';
 }
 
 /// An anchor's private infinite scratchpad: a list of [InkStroke]s in ABSOLUTE