Update documentation for AI SDK v6 APIs and add changeset

[mattpocock]

Parent PRD

#378

What to build

Update all documentation to reflect the v6 migration and add a minor version changeset.

Documentation changes

apps/evalite-docs/src/content/docs/api/ai-sdk.mdx:

• Update wrapAISDKModel() type signature: LanguageModelV2 → LanguageModel
• Replace generateObject/streamObject examples with generateText/streamText + Output.object() pattern
• Ensure all code examples use v6 imports and APIs

apps/evalite-docs/src/content/docs/tips/vercel-ai-sdk.mdx:

• Review for any v5-specific references (type names, deprecated functions)
• Update generateObject examples to generateText + Output.object() pattern
• Ensure integration guide reflects v6 conventions

Changeset

Add a minor version changeset for the evalite package documenting the AI SDK v6 migration. Users on AI SDK v5 should stay on the previous Evalite version.

Acceptance criteria

• api/ai-sdk.mdx shows LanguageModel (not LanguageModelV2) in type signatures
• api/ai-sdk.mdx examples use generateText + Output.object() instead of generateObject
• tips/vercel-ai-sdk.mdx reviewed and updated for v6 (no generateObject/streamObject references)
• Changeset file added with minor bump for evalite package
• Documentation builds without errors

Blocked by

• Blocked by Migrate scorers, test fixtures, and examples to v6 APIs #380

User stories addressed

• User story 7: wrapAISDKModel() API reference shows correct v6 type signature
• User story 8: "Works With All AI SDK Methods" docs show generateText + Output.object() pattern

[mattpocock]

All acceptance criteria met:

• ✅ api/ai-sdk.mdx shows LanguageModel (not LanguageModelV2) in type signatures
• ✅ api/ai-sdk.mdx examples use generateText + Output.object() instead of generateObject
• ✅ tips/vercel-ai-sdk.mdx reviewed — already v6-compatible (no generateObject/streamObject references)
• ✅ Changeset file added with minor bump for evalite package
• ✅ Build passes (pre-existing test failures unrelated to these changes)

Commit: 4e18236