Pipeline E2E Test
Source HTML (3 iframes, 1 bg video, 5 imgs, 2 anchors)
1. Background video (autoplay+loop+muted - keep untouched)
2. YouTube iframes (5 total - 3 budget + 2 lite-embed)
3. Images (no loading attribute - will get added)
4. External anchors (target=_blank, no rel - will get rel=noopener)
External link 1
External link 2
5. YouTube BG iframe (autoplay=1 in src - keep untouched)