Implement accessible smooth scrolling for internal anchor links in Frontblocks.

[Castellon-ACM]

Context

Frontblocks should support smooth scrolling for same-page anchor links, especially for landing pages, documentation pages, and block-based layouts.

The implementation should follow accessibility best practices described here:

https://css-tricks.com/smooth-scrolling-accessibility/

Requirements

• Add smooth scrolling for same-page anchor links.
• Only target valid internal hash links.
• Ignore external links.
• Ignore empty hashes such as # and #0.
• Respect prefers-reduced-motion.
• Ensure keyboard focus moves to the target element after scrolling.
• If the target element is not naturally focusable, temporarily add tabindex="-1" before focusing it.
• Preserve or update the URL hash correctly.
• Avoid issues with sticky headers.
• Keep the implementation lightweight and dependency-free.

Suggested approach

Use native CSS when possible:

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}