Add fixed GRPO training notebook (grpo_training2.ipynb)

Add clean training summary cell to GRPO notebook

Add GRPO fine-tuning notebook for Qwen3.5-0.8B

Finalize demo flow and training assets

Add MOD 08 schema tests, V2 training stack, and close MOD 08/JDG 07/API 01/OBS 02

Complete FND 01 and FND 10, update task division with status tracking