fix: Zod 4 compatibility for prefault, transform pipes, and refined schema omit

[MendyLanda]

Summary

Fixes compatibility issues when using trpc-to-openapi with Zod 4:

• prefault type support: Zod 4 introduces a prefault type (similar to default). Added handling in unwrapZodType to unwrap it via .unwrap(), matching the existing default behavior.
• .transform() pipe handling: In Zod 4, .transform().superRefine() creates a pipe where def.out is an opaque transform type rather than a usable schema. When this is detected, the unwrapper now follows def.in (the input schema shape) instead.
• Refined schema .omit() fallback: Zod 4 throws when calling .omit() on object schemas that have refinements. Wrapped the .omit() call in getRequestBodyObject with a try/catch that falls back to manually filtering path parameter keys from schema.shape.

Fixes #153

Test plan

• Verify unwrapZodType correctly unwraps z.prefault() schemas
• Verify unwrapZodType follows def.in for pipes where def.out is a transform
• Verify getRequestBodyObject works with refined object schemas that have path parameters
• Verify existing behavior is unchanged for non-Zod-4 usage patterns

[mcgilly17]

Would love to see this merged if possible.

[masterjanic]

@mcampa Any chance to get this merged?

[MendyLanda]

To everyone waiting for the merge, just give this pr link to your agent of choice and ask it to patch it for you.

[mcampa]

Hey, Sorry I haven't have time to look at PRs here. Going to merge it and publish a release

[masterjanic]

trpc-to-openapi@3.1.0.patch

I will leave this here for other people. If you are using bun just create a folder patches at the root of your project with the file and append this to package.json

  "patchedDependencies": {
    "trpc-to-openapi@3.1.0": "patches/trpc-to-openapi@3.1.0.patch"
  }

[mcampa]

Published trpc-to-openapi@3.2.0
https://github.com/mcampa/trpc-to-openapi/actions/runs/23318681611/job/67825281102