Remix single fetch: returning submission.reply() with action results in type never.

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Describe the bug and the expected behavior

remix-run/remix#9374

Conform version

v1.1.3

Steps to Reproduce the Bug or Issue

https://stackblitz.com/~/github.com/coji/conform-on-remix-single-fetch

What browsers are you seeing the problem on?

Chrome

Screenshots or Videos

Additional context

I have also raised it as a remix issue. I think it may be a type definition problem on the remix side.
remix-run/remix#9374

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I've received feedback from several users about an issue with SubmissionResult's prop Result<string, unknown>. The unknown type is problematic because it introduces uncertainty about serializability by turbo-stream, which could lead to runtime errors.
remix-run/remix#9374 (comment)

To address this, it's recommended to replace unknown with a more specific type that turbo-stream can reliably serialize. This will improve type safety and prevent potential issues.
However, I'm not quite sure how to best implement this change while maintaining compatibility and avoiding any unintended consequences. I would greatly appreciate your guidance on the most appropriate way to refactor the code to resolve this problem.

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I've updated to remix v2.9.2 and the type error is gone,
However, the newly introduced defineAction / defineLoader still seems to cause type errors due to Result<string, unknown>.

remix-run/remix#9374 (comment)