feat(web): don't scroll to visible assets (#20729)

The timeline has been quite aggressive with scrolling to assets, even if they
were right in the middle of the page. If the asset is visible, then we
shouldn't scroll to it. It's really confusing when assets jump around after
being viewed.

web/src/lib/components/photos-page/asset-grid.svelte

@@ -149,12 +149,28 @@
     return height;
   };
 
+  const assetIsVisible = (assetTop: number): boolean => {
+    if (!element) {
+      return false;
+    }
+
+    const { clientHeight, scrollTop } = element;
+    return assetTop >= scrollTop && assetTop < scrollTop + clientHeight;
+  };
+
   const scrollToAssetId = async (assetId: string) => {
     const monthGroup = await timelineManager.findMonthGroupForAsset(assetId);
     if (!monthGroup) {
       return false;
     }
+
     const height = getAssetHeight(assetId, monthGroup);
+
+    // If the asset is already visible, then don't scroll.
+    if (assetIsVisible(height)) {
+      return true;
+    }
+
     scrollTo(height);
     updateSlidingWindow();
     return true;