Still generate tests when no modelsUnderTest specified

[bzorn]

When no MUTs are specified the paper script terminates with an error message. It should generate the tests.csv file in any case.

❌ Errors
</summary>

-   Error: no modelsUnderTest provided for evaluation
-   no modelsUnderTest provided for evaluation
> ```````markdown> Error: no modelsUnderTest provided for evaluation
>     at file:///home/zorn/promptpex-zoo/promptpex/src/genaisrc/paper.genai.mts?tsx-namespace=1743792677405:1:3158
> ```````

[bzorn]

Paper script no longer used.