Curated Hyperon Prime Index subtopic cardtype. Renders via IndexSubtopic+*type+*structure, which pulls per-field sibling subcards (+responsible, +approval, +description, +github, +docs, +examples, +roadmap, +deep_dive) plus the standard +tags / +discussion wrappers. Companion to IndexSection for section-landing cards. Both share editorial behavior via Abstract::EditoriallyReviewed. Cardtype name matches Sandra's SubTopic data-model term in wikiContent.ts.