feat: add Field Systems reference index

[CoreweaverLabs]

Summary

• add the real /field-systems/ static reference index
• link contextual application questions to the Coreweaver ARM primitives
• include source context, explicit non-claims, metadata, JSON-LD, sitemap, llms inventory, and an editorial release packet

Review status

• desktop and 375×812 local renders reviewed
• static preflight and route-inventory checks passed
• an anonymous temporary preview is available for review

Release boundary

• no VPS provisioned
• no DNS, TLS, canonical host, or Vercel routing changed
• the future public hostname requires explicit provider and DNS/TLS approval