Measure Search and inference usage in the Groq agent

[georgeatparallel]

Summary

• Migrate the existing Groq/Vercel AI SDK agent from legacy beta Search to GA Search.
• Report measured Search latency and retrieved context, provider-reported model tokens, and clearly labeled configurable cost estimates in the existing stream and UI.
• Preserve streaming and make deterministic tests work on Node 20, 22, and 24 without changing package-wide module configuration.

Validation

• npm test: 5 tests passing on Node 20, 22, and 24.
• Strict economics-module typecheck and complete Worker typecheck.
• Wrangler dry-run bundle succeeds without deploying.
• One bounded live Turbo Search request returned one result and one Search SKU.