fix: prevent anchor links from navigating away from HIP detail view

[mgarbs]

Summary

• Fix TOC sidebar links and in-body anchor links (e.g. [Motivation](#motivation)) on HIP detail pages navigating back to the HIPs list instead of scrolling to the target section

Root Cause

The site uses hash-based routing (#hip-123, #about, etc.) with a hashchange listener that calls handleRoute(). When a TOC or in-body anchor link like #motivation is clicked, it changes location.hash, which triggers handleRoute. Since #motivation doesn't match any known route pattern (#hip-*, #about, #create), it falls through to the default case which shows the list view — navigating the user away from the HIP they were reading.

Fix

Intercept clicks on both TOC links and in-body anchor links with preventDefault(), then use scrollIntoView({ behavior: 'smooth' }) to scroll to the target heading without changing the hash or triggering the router.

Test plan

• Open any HIP with a TOC (e.g. HIP-1) → click a TOC entry → page scrolls to that section without leaving the detail view
• Click an in-body anchor link within a HIP's markdown content → same smooth scroll behavior
• Normal navigation still works: back link, nav links, clicking other HIPs

🤖 Generated with Claude Code

[Reccetech]

Approved.