feat: 🎸 make /first-rows depend on /split-names, not /splits
`/splits` fails if any config is broken. By depending on `/split-names`, the working configs will have `/first-rows`.

Follow-up to #702
feat: 🎸 make /first-rows depend on /split-names, not /splits: `/splits` fails if any config is broken. By depending on `/split-names`, the working configs will have `/first-rows`.

Follow-up to #702