Keep your dataset small and focused.

### Pretrain (`corpus_raw.txt`)
Short concept notes you wrote yourself (or public domain). Aim 0.5–5 MB:
- definitions (inertia, momentum, energy…)
- short derivations (one paragraph)
- worked mini examples (1–3 lines)

### SFT (`sft_train.jsonl`)
Each line: {"instruction": "...", "output": "..."}
Keep answers short and factual. 200–1000 examples is fine.

**Do not include copyrighted textbook dumps.**