The social media thumbnail (public/assets/thumbnail.jpg) is a screenshot of the homepage's first screen:
- Open the homepage in a 1200 × 630 viewport (light scheme, scrollbars hidden), at 2× device scale.
- Take a viewport screenshot and downscale it to 1200 × 630.
- Save it as a JPEG under 100 KB (mozjpeg quality 80 lands near 40 KB).
These dimensions follow the Next.js documentation recommendations for social media thumbnails/OG images.