Archive self-play beans, update shader/LLM parent beans to completed,
and add self-play chapter content to ml-self-play.md.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Adds llm-from-scratch.md stub with 14 sections (GPT-1 style: character
tokenisation, self-attention, transformer block, candle model, training
loop, sampling). Creates beans edu-32xl through edu-9sb7 for each section.