performance improvements + ui/ux fixes

src/navigation/tabTransition.ts

@@ -1,10 +1,11 @@
 /**
  * Bottom tabs use React Native's legacy native Animated driver. On Android,
- * timing animations are pre-sampled at 60 fps, so their positions repeat on a
- * 120 Hz display. A critically damped native spring is evaluated from each
- * display frame instead while preserving the current ~160 ms ease-out feel.
+ * timing animations are pre-sampled at 60 fps. A short, critically damped
+ * native spring avoids translating two retained full-page scenes and leaves
+ * only an intentional cross-fade at the tab boundary.
  */
 export const TAB_TRANSITION_SETTLE_MS = 160;
+export const TAB_SCENE_ANIMATION = 'fade' as const;
 
 export const TAB_TRANSITION_SPEC = {
   animation: 'spring',
@@ -17,4 +18,3 @@ export const TAB_TRANSITION_SPEC = {
     restSpeedThreshold: 0.15,
   },
 } as const;
-