chore: root_plate_* — cce-ui 7a-2 caller migration

Mechanical rename onto cce-ui's canonical root-plate getters
(cce-ui@c8e0ab3, RFC Phase 7a); behavior unchanged, same config slots.

 src/main.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index e9aeabb..1462832 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1185,10 +1185,10 @@ impl Application for GraphApp {
             use cce_ui::scene::layout::Rect;
             let mut plate_color = cce_ui::color::page_low_color();
             if plate_color[3] > 0.001 {
-                plate_color[3] = cce_ui::color::active_backplate_opacity();
+                plate_color[3] = cce_ui::color::root_plate_opacity();
             }
             let rect = Rect { x: 0.0, y: 0.0, width: self.width as f32, height: self.height as f32 };
-            let radius = cce_ui::colors::backplate_corner_radius();
+            let radius = cce_ui::colors::root_plate_corner_radius();
             if radius > 0.1 {
                 pc.rounded_rect(rect, radius, (true, true, true, true), plate_color);
             } else if plate_color[3] > 0.001 {