Space T4 + real HF path: split requirements, GPU defaults, API reset behavior

Finalize eval-friendly defaults: offline baseline, deterministic API reset, docs cleanup

Add story blog updates and submission-ready docs links

fix(hf-cpu): slim requirements.txt for Spaces; requirements-train.txt for PyTorch/TRL; suggested_hardware cpu-basic

Add Dockerfile, Docker Compose, and GitHub Action to publish Docker image to GHCR