feat(render): logical style metrics with a UI scale, so chrome has a consistent physical size

adapters/qt6/qt_plot_widget.cpp

@@ -179,6 +179,11 @@ void PlotWidget::paintGL() {
   last_paint_s_ = started;
   if (frame_) frame_(*plot_, dt);
 
+  // The same factor `device_viewport()` scales the widget by: it states the display
+  // for the renderer too, so the logical style metrics are drawn at this ratio and
+  // a 12 px label keeps its physical size on a 2x screen. Re-read every frame, like
+  // the viewport, so a window moved to another display is drawn at *its* scale.
+  renderer_->style().ui_scale = static_cast<f32>(devicePixelRatioF());
   renderer_->begin_frame(static_cast<u32>(viewport.w), static_cast<u32>(viewport.h), viewport);
   renderer_->draw(*plot_);
   renderer_->end_frame();