docs: add TOC minimap + mobile nav and heading anchors

[phh235]

What does this PR do?

Adds a TOC minimap (desktop hover card) and mobile accordion for on-page section navigation across all component doc pages. The TOC is lifted out of component-doc into the shell layout with position: fixed, so demo wrappers like ClothDemo no longer squeeze or affect its positioning. Introduces a TOCContext to share TOC items from the server-side component-doc to the client-side layout components without prop drilling.

Also adds a reusable HeadingAnchor component for scrollable heading links, a demoSection prop for including "Demo" in the TOC, and fixes the hover card's positionMethod to "fixed" to prevent floating-UI repositioning during programmatic smooth scroll.

Additionally, updates the previous/next navigation button layout to improve visual balance and consistency with the new documentation navigation experience.

Demo

2026-07-26.21-50-58.mp4

Updated navigation buttons

Type of change

• Docs / site

Checklist

• npx tsc --noEmit passes
• npm run lint passes
• npm run build passes
• Tested in Chrome (with the html-in-canvas flag, if relevant)
• Tested the WebGL overlay fallback (flag off / Safari / Firefox), if a component changed

[DavidHDev]

I'm sorry but I'm not a big fan of this kind of docs feature, I think it only adds complexity to a perfectly simple page, which isn't really needed, because there's not that much to scroll.

Please open issues before implementing such design choices, I don't want to waste your time.

[phh235]

I'm sorry but I'm not a big fan of this kind of docs feature, I think it only adds complexity to a perfectly simple page, which isn't really needed, because there's not that much to scroll.

Please open issues before implementing such design choices, I don't want to waste your time.

I got it sir!