7 — Move model index inline styles to component

Problem: docs/model/index.md has 345 lines of inline <style> — the largest inline style block in any markdown file. Hard to maintain, no scoping, no IDE support.

Action:

• Create .vitepress/theme/components/ModelLanding.vue component
• Move the HTML structure and styles from index.md into the component
• index.md becomes <ModelLanding />

Files touched:

• .vitepress/theme/components/ModelLanding.vue (new)
• .vitepress/theme/index.ts (register component)
• docs/model/index.md

Done when: docs/model/index.md has zero inline CSS. All model landing styles are scoped.