feat(amazon-bedrock): add guardrail content support for text and image parts

[raphaeleidus]

Background

The Amazon Bedrock Converse API supports guardrail content blocks that allow marking text and image parts for guardrail evaluation with optional qualifiers (grounding_source, query, guard_content). The existing BedrockGuardrailConverseContentBlock type was untyped (guardContent: unknown) and there was no way to opt into this behavior from the AI SDK.

Documentation on the Bedrock Feature

Summary

• Added BedrockGuardrailTextBlock type extending BedrockTextBlock with optional qualifiers array.
• Typed BedrockGuardrailConverseContentBlock.guardContent as a union of text and image variants instead of unknown.
• Added Zod schemas (bedrockTextPartProviderOptions, bedrockImagePartProviderOptions) for validating provider options, used via parseProviderOptions consistent with existing patterns.
• Users can now set providerOptions.bedrock.guardContent: true on text and image parts to wrap them as guardContent blocks, with optional guardContentQualifiers for text parts.
• Added 8 tests covering text guard content (with/without qualifiers, false, no options) and image guard content (true, false, no options).

Checklist

• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added (for bug fixes / features - run pnpm changeset in the project root)
• I have reviewed this pull request (self-review)

[raphaeleidus]

@aayush-kapoor could I trouble you to look this over?
Is there any additional context you might need here?

[aayush-kapoor]

not context but this implementation will need some actual examples + a UI example that will test for multiturn conversations + tests and fixtures possibly returned by bedrock to see what it responds with.