Address Stale lastSeenValueRef causes visual regression on re-entry

When the targetValue changes while the element is out of viewport, the
else-if branch (lines 96-100) correctly snaps the display to the new
target but fails to clear lastSeenValueRef. This ref retains a stale
mid-animation value from when the element exited viewport. When the
element later re-enters viewport, the condition at line 88 evaluates
true (stale value differs from new target), causing the animation to
start from the old saved value instead of the current displayed value.
This produces a visible backward jump in the counter before it animates
forward.

Author: jsoningram

special-pages/pages/new-tab/app/protections/utils/useAnimatedCount.js

@@ -148,6 +148,9 @@ export function useAnimatedCount(targetValue, elementRef) {
             // This handles the case where value changes while element is out of viewport
             setAnimatedValue(targetValue);
             animatedValueRef.current = targetValue;
+            // Clear lastSeenValueRef since we've updated to the new target
+            // This prevents stale values from causing backward jumps on re-entry
+            lastSeenValueRef.current = null;
         }
         // else: conditions not met and haven't animated yet, do nothing (wait for viewport entry)
 
@@ -164,6 +167,8 @@ export function useAnimatedCount(targetValue, elementRef) {
                 if (hasAnimatedRef.current) {
                     setAnimatedValue(targetValue);
                     animatedValueRef.current = targetValue;
+                    // Clear lastSeenValueRef since we've updated to the current target
+                    lastSeenValueRef.current = null;
                 }
             }
         };