[breaking] Anthropic deprecates Claude Opus 4.1, retirement August 2026

claude-opus-4-1-20250805 was deprecated June 5, 2026 and retires August 5, 2026. Recommended replacement: claude-opus-4-8. Effective: 2026-08-05. Migration target: anthropic/claude-opus-4-8. Affected: anthropic/claude-opus-4-1-20250805. Severity: breaking. Verification: verified.