fix: show predictive back affordance for settings overlay

code/th_02_core.js

@@ -43,6 +43,8 @@ function FloatBallAppWM(logger) {
     viewerPanelLp: null,
     viewerPanelType: null,
     panelBackCallbackEntries: [],
+    predictiveBackIndicatorView: null,
+    predictiveBackIndicatorLp: null,
 
     // 设置类 UI App 化：单窗口页面栈（settings -> 子页面 -> 编辑页）
     toolAppActive: false,