Add Google Colab Sudoku 1k demo (T4-compatible)

[mohabedalgani]

What

• One-click Colab notebook that reproduces the Sudoku-Extreme 1 k experiment on a free T4 GPU (~55 min).
• Fixes #0 (no open issue, but fills a gap in quick-start docs).

How tested

• Ran end-to-end in Colab PRO high-ram today → final exact accuracy: 99.3 % (see notebook).
• Badge uses relative link so it will work after merge.

Files changed

• notebooks/colab/HRM_Sudoku_1k_T4.ipynb (new)
• README.md (one extra line)

[imoneoi]

Thanks for the PR! 99.3% seems amazing, it's much higher than reported in our paper. Is that result from evaluate.py? I can't find the result of evaluation cell in the notebook.

[benman1]

This runs but I've never managed to get any correct examples in test in spite of trying. The model architecture is completely different. This is just a generic transformer model.