The Hub counts a model download for every request to a root `config.json`; the repo has only `.pth` files, so DeFM currently shows 0 downloads. This adds a `config.json` with the architecture config of all 12 variants (generated from `defm/configs/*.yaml` by `scripts/hf/build_model_config.py`). Nothing reads it yet; the defm package will fetch it before the weights from the next release. No existing file changes.
