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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index ecfb766..1298254 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -683,7 +683,7 @@ impl Application for AuthenticatorApp {
         // which merges a per-app override the compositor never sees.
         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 wr = cce_ui::layout::window_corner_radius().max(0.0);
         pc.plate(