Add tests for `numericIdZodType` utility

[Zod](https://zod.dev/) is a library for validating and parsing data. `numericIdZodType` is a utility we use to validate and parse numeric IDs, it accepts positive integers or the string representation of a positive integer.

This issue involves adding a file `workspaces/util/src/__tests__/numericIdZodType-test.ts`, for testing the `numericIdZodType` utility. Specifically, we care about testing the `parse` function, so stuff like:

```ts
expect(numericIdZodType.parse(123)).toBe(123);
expect(() => numericIdZodType.parse(-123)).toThrow(/* some error */);
```

To see some PRs that add tests, take a look at #288 and #290 for inspiration.

Create workspaces/util/src/__tests__/numericIdZodType-test.ts and inspect numericIdZodType plus the test patterns in PRs #288 and #290. Exercise its parse function with positive integer numbers and string representations, and verify that negative values are rejected. Done means the utility's stated accepted and rejected inputs are covered.

Written by the indexing model from the issue text.