fix(lazy-images): serialize position object to string in returned items

Author: nucliweb

.claude/skills/webperf-loading/scripts/Find-Above-The-Fold-Lazy-Loaded-Images.js

@@ -135,7 +135,7 @@
       selector: image.selector,
       lazyType: image.lazyType,
       dimensions: image.dimensions,
-      position: image.position,
+      position: `${image.position.top}px, ${image.position.left}px`,
       distanceFromEdge: image.distanceFromEdge,
       src: image.src,
       srcset: image.srcset,

dist/webperf-loading/Find-Above-The-Fold-Lazy-Loaded-Images.js

@@ -246,7 +246,7 @@
       selector: image.selector,
       lazyType: image.lazyType,
       dimensions: image.dimensions,
-      position: image.position,
+      position: `${image.position.top}px, ${image.position.left}px`,
       distanceFromEdge: image.distanceFromEdge,
       src: image.src,
       srcset: image.srcset,