[breaking] Amazon Bedrock retires Claude Sonnet 4 (EOL 2026-10-14)

Amazon Bedrock moves Anthropic Claude Sonnet 4 to Legacy on 2026-04-14 with end-of-life on 2026-10-14 (public extended access from 2026-07-14, at provider-set pricing). Bedrock lifecycle dates are platform-specific and may differ from the model provider's own schedule. announced_at reflects the documented Legacy date, when Bedrock notifies users. Effective: 2026-10-14. Affected: amazon/anthropic.claude-sonnet-4-20250514-v1:0. Severity: breaking. Verification: verified.