feat(v2): update train_grpo.py for step-level prompts and per_step_reward

feat(v2): add extract_crease_json and valid_crease reward to training/reward.py

feat: expand reward pipeline and GRPO training config

revert: restore train_origami.ipynb to Prasanna's exact version

chore: restore Prasanna's notebook, add Modal launch section

feat: Railway deployment + multi-task GRPO + Modal B200 training

Update training notebook

Add MAX_CONCURRENT_ENVS, sync latest changes

Add GRPO training notebook + Dockerfile for cloud training (#1)

Rename server/ to origami_server/ to avoid module name conflict with uvicorn.server

Origami RL environment with Three.js viewer