Fix root endpoint: use middleware to serve / (openenv-core intercepts route-level handler)

Add root endpoint so HF Spaces visitors see environment info instead of 404

Ignore PDF files for HF Spaces deployment

HF Spaces deployment: add YAML frontmatter, Dockerfile non-root user, .gitignore cleanup

Rewrite training pipeline: env-in-the-loop rewards, multi-turn prompts, all difficulty levels

v2.1: OpenEnv 0.2.1 integration + training notebook + HF Spaces deployment

v2.0: Novel world types + adversarial self-play for hackathon win

Hypothesis Engine: Scientific Discovery RL Environment for LLM Training