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.
Add shaders.md with 18 stub sections across 6 parts (GPU model,
wgpu setup, vertex/fragment shaders, textures, compute shaders,
going further). Create beans tickets edu-5g0l through edu-7m8d
for each section. Add # Graphics section to SUMMARY.md.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>