fix: discriminatedUnion format handling

[wststone]

• Update formatZodType and extractPropsFromSchema in
  catalog.ts to work with Zod v4's internal _def structure
• discriminatedUnion now correctly resolves literal types
  (was showing type: undefined)
• Add tests for discriminatedUnion and nativeEnum in prompt
  generation

[vercel]

@wststone is attempting to deploy a commit to the Vercel Labs Team on Vercel.

A member of the Team first needs to authorize it.