fix: PDF finger ink, chrome UX, OneNote pens, and pen physics

Wire finger drawing on PDF without breaking pinch; auto-hide page scrubber and fix bounce; share sticky tools with resize and per-page remember; side-button select; separate pen slots with colors; rnote pressure shapes plus tip-velocity width and lower stroke latency.

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

lib/editor/ui/pen_settings_page.dart

@@ -1,6 +1,25 @@
 import 'package:flutter/material.dart';
 
 import '../input/pen_config.dart';
+import '../input/pressure_curve.dart';
+
+String _shapeNameForGamma(double gamma) {
+  if ((gamma - 0.6).abs() < 0.05) return 'soft';
+  if ((gamma - 1.0).abs() < 0.05) return 'linear';
+  if ((gamma - 2.0).abs() < 0.05) return 'quadratic';
+  if ((gamma - 3.0).abs() < 0.05) return 'cubic';
+  if ((gamma - 0.5).abs() < 0.05) return 'sqrt';
+  return 'soft';
+}
+
+PressureCurve _curveForName(String name) => switch (name) {
+      'linear' => PressureCurve.shaped(PressureCurveShape.linear),
+      'quadratic' => PressureCurve.shaped(PressureCurveShape.quadratic),
+      'cubic' => PressureCurve.shaped(PressureCurveShape.cubic),
+      'sqrt' => PressureCurve.shaped(PressureCurveShape.sqrt),
+      'logarithmic' => PressureCurve.shaped(PressureCurveShape.soft), // gamma proxy
+      _ => PressureCurve.shaped(PressureCurveShape.soft),
+    };
 
 /// Shows a Material You modal bottom sheet for configuring pen input.
 ///
@@ -111,6 +130,32 @@ class _PenSettingsSheet extends StatelessWidget {
                   formatValue: (v) => v.toStringAsFixed(2),
                   onChanged: controller.setPressureGamma,
                 ),
+                _LabeledRow(
+                  label: 'Curve Preset (rnote)',
+                  child: DropdownMenu<String>(
+                    initialSelection: _shapeNameForGamma(config.pressureGamma),
+                    onSelected: (name) {
+                      if (name == null) return;
+                      final shaped = _curveForName(name);
+                      controller.setPressureGamma(shaped.gamma);
+                    },
+                    dropdownMenuEntries: const [
+                      DropdownMenuEntry(value: 'soft', label: 'Soft (γ≈0.6)'),
+                      DropdownMenuEntry(value: 'linear', label: 'Linear'),
+                      DropdownMenuEntry(
+                          value: 'quadratic', label: 'Quadratic / Pow2'),
+                      DropdownMenuEntry(value: 'cubic', label: 'Cubic'),
+                      DropdownMenuEntry(value: 'sqrt', label: 'Sqrt (pencil)'),
+                    ],
+                  ),
+                ),
+                const Padding(
+                  padding: EdgeInsets.only(left: 8, bottom: 8),
+                  child: Text(
+                    '笔刷自带曲线优先（钢笔=二次/Pow2，铅笔=平方根）。全局 gamma 作后备。',
+                    style: TextStyle(fontSize: 12),
+                  ),
+                ),
 
                 // ── Input ─────────────────────────────────────────────────
                 _SectionHeader(
@@ -265,12 +310,13 @@ class _ActionDropdown extends StatelessWidget {
   final ValueChanged<PenButtonAction> onChanged;
 
   static String _label(PenButtonAction action) => switch (action) {
-        PenButtonAction.none => 'None',
-        PenButtonAction.eraser => 'Eraser',
-        PenButtonAction.undo => 'Undo',
-        PenButtonAction.toggleTool => 'Toggle Tool',
-        PenButtonAction.pan => 'Pan',
-        PenButtonAction.selectText => 'Select text',
+        PenButtonAction.none => '无',
+        PenButtonAction.eraser => '橡皮',
+        PenButtonAction.undo => '撤销',
+        PenButtonAction.toggleTool => '切换工具',
+        PenButtonAction.pan => '平移',
+        PenButtonAction.select => '选择（笔迹）',
+        PenButtonAction.selectText => '选择文本',
       };
 
   @override