Add README with base model metadata

Copy config.json from google/gemma-4-31B-it

Upload tokenizer - SAE introspection LoRA - google/gemma-4-31B-it-layers_17-29-47-decoder-True_gemma4_custom - step 125000

SAE introspection LoRA - google/gemma-4-31B-it-layers_17-29-47-decoder-True_gemma4_custom - step 125000

initial commit