feat(ai): add validateUIMessages function

[lgrammel]

Background

Validating UI messages is often necessary, e.g. when they are loaded from the DB or received through REST requests.

Summary

Add validateUIMessages function.

Example

const messages = await validateUIMessages<UseChatToolsMessage>({
  messages: body.messages,
  tools,
});

Manual Verification

• test ui tool calling example with validation

Tasks

• implementation TextUIPart
• implementation ReasoningUIPart
• implementation SourceUrlUIPart
• implementation SourceDocumentUIPart
• implementation FileUIPart
• metadata
• implementation StepStartUIPart
• implementation DataUIPart<DATA_TYPES>
• implementation DynamicToolUIPart
• implementation ToolUIPart
• test provider metadata
• test data ui part missing schema
• documentation (reference)
• documentation (guide)
• example updates
• changeset

Related Issues

Fixes #6763

[imranbarbhuiya]

I tried this here imranbarbhuiya@caccd03#diff-359eed88eef8047dde41894dee7f556365015932d5dfcdb994e5c13db9c2c1fb but there were some deep typing issues in test so I stopped, but it has most of the schemas, u can probably use some from there

[imranbarbhuiya]

since u r using zod v4, u can use

Suggested change

	type: z.string().startsWith('data-'),
	type: z.templateLiteral([z.literal('data-'), z.string()]),

[lgrammel]

and make it less readable when it is not needed? why would i do that?

[imranbarbhuiya]

it gives proper type like the interface currently has data-${string} instead of just string, other then than yeah current one is better readable

[lgrammel]

here we wont push everything into zod because the dynamic union types are too complex, so it doesnt matter, hence the simpler version