feat(amazon-bedrock): add model family setting for embeddings to support ARN (#19854)

## Background

bedrock tried to identify Cohere/Nova from the model ID. Opaque
application profile ARNs contain no model name, so they were mistaken
for Titan, causing the wrong request format and batch size

## Summary

we introduced a new embedding model setting to specify family: 

```ts
amazonBedrock.embedding(profileArn, { modelFamily: 'cohere' })
```

this correctly controls both payload formatting and batching

## End-to-End Verification

needs an account configured with an ARN profile but verified with unit
tests

## Checklist

- [x] All commits are signed (PRs with unsigned commits cannot be
merged)
- [x] Tests have been added / updated (for bug fixes / features)
- [x] Documentation has been added / updated (for bug fixes / features)
- [x] A _patch_ changeset for relevant packages has been added (for bug
fixes / features - run `pnpm changeset` in the project root)
- [x] I have reviewed this pull request (self-review)

## Related Issues

fixes #19829 

closes #19834 

closes #19830