Allow Unchecked Schema for Tool Calls and object generations. Make Zod optional.

[Necmttn]

Feature Description

For the AI core api would like to be able to generate tool calls based on the JSON Schema instead of Zod Schema

Use Case

In @craftgen We are generating the json schema for the nodes/tools on the fly a.k.a user generated.

Additional context

@lgrammel have implemented this before for modelfusion 🤘

https://github.com/vercel/modelfusion/blob/9d99703dc7b60836992bf661cfc9698c8ee5976c/examples/basic/src/model-function/generate-object-unchecked-json-schema-example.ts#L2

Let me know if you guys need help.

[lgrammel]

Duplicates #1062