[breaking] Groq retires llama-3.1-8b-instant and llama-3.3-70b-versatile

Groq shuts down llama-3.1-8b-instant, llama-3.3-70b-versatile on GroqCloud effective 2026-08-16. Users were notified by email on 2026-06-17. Recommended replacements: openai/gpt-oss-20b, openai/gpt-oss-120b. Effective: 2026-08-16. Affected: groq/llama-3.1-8b-instant, groq/llama-3.3-70b-versatile. Severity: breaking. Verification: verified.