Allow throw notFound() in params.parse and validateSearch

[nstepien]

const intRegExp = /^[1-9]\d*$/;

export const Route = createFileRoute('/posts/$postId')({
  params: {
    parse(params) {
      const { postId } = params;

      if (!intRegExp.test(postId)) {
        throw notFound();
      }

      return {
        postId: Number.parseInt(postId, 10)
      };
    },
    stringify(params) {
      return {
        postId: params.postId.toString()
      };
    }
  },
});

I'd love to throw notFound() like in the example above.

We have params we know must be valid integers above 0, UUIDs, or enum values for example.
We run assertions to ensure we can narrow the type correctly when it's passed down to beforeLoad, loader, or accessed via Route.useParams().

Right now we throw an error, which means invalid params will display the error component.
Displaying the error page makes it look like there's a bug in our app, when it's not the case.
Displaying the not found page is what we'd expect, and better communicates to the end user what's happening.
Not sure why it's not allowed currently.