Add a sticky blog article outline

[walishcs]

Summary

• add an Astryx Outline table of contents to blog detail pages
• keep the article body at the existing 47rem reading width
• enable heading scroll spy, smooth anchor navigation, sticky desktop positioning, and mobile hiding
• upgrade Astryx core, CLI, and supported themes to 0.4.4

Validation

• npm run check
• npm test
• npm run format:check
• npm run build
• npm run astryx -- doctor
• verified generated heading IDs match all Outline links on the current Chinese blog article
• verified click offset, scroll spy, sticky layout, 390px mobile hiding, and no horizontal overflow