[breaking] Groq retires moonshotai/kimi-k2-instruct-0905

Groq shut down moonshotai/kimi-k2-instruct-0905 on GroqCloud effective 2026-04-15. Users were notified by email on 2026-03-23. Recommended replacement: openai/gpt-oss-120b. Effective: 2026-04-15. Migration target: groq/openai/gpt-oss-120b. Affected: groq/moonshotai/kimi-k2-instruct-0905. Severity: breaking. Verification: verified.