[BUG] Buggy thumbnail layout in trace viewer and UI mode

[scitech]

System info

• Playwright Version: v1.34.3
• Operating System: macOS
• Browser: All
• Other info:

Source code

Unable to share a reproducer but I can work on it if needed.

Steps

• playwright test --ui

Expected

Thumbnails are laid out in a single horizontal row.

Actual

Thumbnails are in a staggered layout which makes the other panels unusable: