docs: add Qarinah feature discovery surface

[AjnasNB]

What changed

• adds a canonical Qarinah Features page with visible, source-backed capability groups
• exposes Features, Install, and Docs as explicit primary navigation destinations
• adds CollectionPage and ItemList structured data for the visible capability inventory
• includes the page in the generated sitemap, local documentation search, package files, README, and llms.txt
• extends site verification for the new route, links, content, and structured data

Why

Qarinah already had accurate product, installation, and API documentation, but its primary navigation did not expose a dedicated feature destination. This makes the product hierarchy clearer to people and crawlers without adding ranking claims or duplicating the installation guide.

Validation

• npm run check (complete repository gate, including 182 tests, types, MCP smoke, site/docs verification, evidence checks, reproducible evaluations, and package dry-run)
• npm run build:site
• npm run check:site
• npm run check:docs