- satori + sharp generates 1200×630 PNG per post at build time
- Blue gradient background matching sky-blue brand theme
- Chinese font: Noto Sans SC (static, downloaded at build time)
- Layout.astro now emits og:image + twitter:image meta tags
- scripts/download-fonts.sh for CI font provisioning
Closes the social sharing card gap — links shared to WeChat/XHS
now display a proper card with title, description, and branding.
