Replace complex weight restoration workaround with a simple one-line config fix.
The root cause: Step-Audio-EditX model config was missing 'tie_word_embeddings'
setting, so transformers 4.54+ defaulted to True and tied lm_head to embed_tokens
even though the checkpoint has different weights for each.
Solution: Add 'tie_word_embeddings': false to config.json to prevent tying.
This is much simpler and cleaner than the previous safetensors weight restoration
approach. One line in config.json fixes the issue for all transformers versions.