feat(field): FIELDDISPLAY gray field background (screen only, profile setting)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/update/file.rs

@@ -677,6 +677,7 @@ impl OpenCADStudio {
             grip_object_limit: self.grip_object_limit,
             image_frame: crate::scene::frame::profile_image_mode(),
             attdef_on_screen: crate::modules::draw::draw::attdef::session().on_screen,
+            field_display: crate::entities::field::display(),
             ncopy_bind: self.ncopy_bind,
             cursor_type: self.cursor_type,
             crosshair_color: self.crosshair_color,
@@ -771,6 +772,7 @@ impl OpenCADStudio {
         self.grip_object_limit = s.grip_object_limit.clamp(0, 32767);
         crate::scene::frame::set_profile_image_mode(s.image_frame);
         crate::modules::draw::draw::attdef::session().on_screen = s.attdef_on_screen;
+        crate::entities::field::set_display(s.field_display);
         self.ncopy_bind = s.ncopy_bind;
         self.cursor_type = s.cursor_type;
         self.crosshair_color = s.crosshair_color;