Polish ecosystem showcase for launch

[EmersonBraun]

Summary

• add recognizable product marks to all six public ecosystem tabs
• make CTA destinations explicit and route product discovery CTAs to each product home
• keep the canonical ecosystem contract, generated copies, and documentation evidence synchronized

Validation

• pnpm test:ecosystem
• pnpm test:ecosystem-doc-quality
• pnpm check:readme-standard
• pnpm test:readme-standard
• pre-push quality gates
• browser checks at 1100px and 390px: six marks, canonical Registry CTA, no horizontal overflow

Vercel previews remain disabled for this branch by the repository policy.

[github-actions]

Lighthouse

URL	Performance	Accessibility	Best practices	SEO
http://127.0.0.1:3000/	77	92	96	100
http://127.0.0.1:3000/docs	70	100	96	100
http://127.0.0.1:3000/docs/get-started/getting-started/quickstart	71	96	96	100
http://127.0.0.1:3000/stack	90	100	96	100
http://127.0.0.1:3000/showcase	94	100	96	100

Run by .github/workflows/lighthouse.yml.