## Motivation

Often the summary of average/max/min reward is not enough information,
and it's helpful to look at some real-world generations to see how the
model's actual behavior is changing over time. This can be particularly
helpful for debugging issues like the generation being cut off before
reasoning finishes.

## Change

This PR introduces a new `trainer.val_generations_to_log_to_wandb`
config value, with a default of 0. If set to a number larger than 0, it
logs that number of inputs/outputs/scores each time the validation set
is generated and scored. It uses a [wandb
Table](https://docs.wandb.ai/guides/track/log/log-tables/) to do so,
adding a single row for each validation set run.

I choose to log the data in this format because it allows a user to
easily see how the outputs for a given input change over time by looking
down a column vertically.

## Screenshot

<img width="1106" alt="Screenshot 2025-01-31 at 8 02 47 AM"
src="https://github.com/user-attachments/assets/f2ec0079-8464-4735-ad63-d71f349f4332"
/>

Note: if there's already another way to accomplish this easily let me
know! I was surprised not to find a way to see sample generations
because I find that quite useful, so let me know if I'm missing
something.