## Problem

The Bedrock `invoke` path does not support native structured output (`response_format`) for Claude models that have this capability. Callers using `bedrock/anthropic.claude-*` with `response_format` either get an error or fall through to tool-call emulation, even for models that support Anthropic's native `output_format` API via Bedrock.

## Proposed fix

Add `response_format` handling to the Bedrock invoke transformation for Claude models with `supports_output_config: true`. Map `response_format` to the appropriate Anthropic `output_format` field in the Bedrock request body, matching the behavior already present in the direct Anthropic provider path.

## Files

- `litellm/llms/bedrock/` (invoke transformation)