fix(canvas): persist strokes, pressure, slider

Strokes vanished on pen-up: StaticInkPainter aliased the same mutable
list so shouldRepaint saw no change. Commit/erase now replace the list.
Finger-drawing toggle wins over palm-rejection; pressure surfaces even
when the pen reports no min/max range; pages recenter after a flip; the
keyboard page-jump (unreliable on Windows) is now a drag slider. Also
register the dynamic_color plugin in generated registrants.

windows/flutter/generated_plugin_registrant.cc

@@ -6,12 +6,15 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <dynamic_color/dynamic_color_plugin_c_api.h>
 #include <file_selector_windows/file_selector_windows.h>
 #include <flutter_onnxruntime/flutter_onnxruntime_plugin.h>
 #include <syncfusion_pdfviewer_windows/syncfusion_pdfviewer_windows_plugin.h>
 #include <url_launcher_windows/url_launcher_windows.h>
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {
+  DynamicColorPluginCApiRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("DynamicColorPluginCApi"));
   FileSelectorWindowsRegisterWithRegistrar(
       registry->GetRegistrarForPlugin("FileSelectorWindows"));
   FlutterOnnxruntimePluginRegisterWithRegistrar(

windows/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  dynamic_color
   file_selector_windows
   flutter_onnxruntime
   syncfusion_pdfviewer_windows