docs(ads): clarify ad disposal logic in InArticleAdLoaderWidget

Updated the comment in the `dispose` method of `InArticleAdLoaderWidget` to be more explicit about why the ad object is not disposed of there. This reinforces that the ad's lifecycle is managed by the `InlineAdCacheService` and that disposal only happens when the entire article context is cleared.

Author: fulleni

lib/ads/widgets/in_article_ad_loader_widget.dart

@@ -118,11 +118,12 @@ class _InArticleAdLoaderWidgetState extends State<InArticleAdLoaderWidget> {
 
   @override
   void dispose() {
-    // The ad is intentionally not disposed of here. The InlineAdCacheService
-    // is responsible for managing the ad's lifecycle. The cache for an
-    // article context is cleared when the user navigates away from the
-    // article details page, which is handled by other parts of the app
-    // (e.g., a higher-level widget's dispose method).
+    // The ad object (_loadedAd) is intentionally not disposed of here.
+    // Its lifecycle is managed by the InlineAdCacheService. The cache for this
+    // article's context is cleared when the user navigates away from the
+    // article details page, which is the correct and only time these in-article
+    // ads should be disposed. This prevents ads from being destroyed when they
+    // are part of a list that scrolls out of view.
     if (_loadAdCompleter != null && !_loadAdCompleter!.isCompleted) {
       // Complete normally to prevent crashes
       _loadAdCompleter!.complete();