laravel/ai: Structured output now works on Bedrock models that reject forced tool choice
Structured output on Amazon Bedrock broke for the newest Anthropic models, and PR #1104 brings it back. Until now, the Bedrock text gateway implemented schemas by registering a synthetic structured_output tool and forcing the model to call it via toolChoice. Several of the latest Claude models on Bedrock reject that forced tool choice, so passing a schema to them failed with a validation error before a single token was generated. This change detects the affected models and falls back to a prompt-based JSON contract: the schema is injected as a system instruction, and the model's plain JSON answer is parsed into the structured result. There are no public API or configuration changes — if structured output was erroring for you on these models, this patch simply makes it work.
