Disclose KHIPU-R2 abstain job; never overwrite signed 1.5B

feat(train): abstain retrain to KHIPU-R2, keep ATELIER card

feat(train): KHIPU-R2 Unsloth QLoRA on doctrine SFT + ouroboros identity, szl-forge knobs

docs(card): Series A KHIPU-R2 lookbook card — cutting, no weights yet

initial commit