beautifulprompt PPO can't find pytorch_model.bin

When i running the PPO code, is it necessary to look for the `pytorch_model.bin` file in the `output/sft` folder, but only a single model file `model.safetensors` is saved after `sft`, causing the PPO script to fail to run?

Start with the PPO code path that reads the checkpoint from output/sft, then compare its expectation of pytorch_model.bin with the model.safetensors file produced after SFT. Run the PPO flow against the generated output/sft checkpoint; done means it can load that checkpoint and proceed without the current missing-file failure.

Written by the indexing model from the issue text.