Adds the data-generation code for every task.
- `<task>/script.py` for all 30 tasks: the generator that produced each task's `data/` and `data.json`. `colours_present/script.py` includes the fix from #2 (gold vector built from a list in `rules.txt` order).
- `swatches.png` in `colours_present`, `layered_colours` and `list_colours`: the colour reference strip these generators append below each image (pixel-identical to the strip in the released images).
- `README.md`: `script.py` is added to the layout, and a new "Regenerating the data" section gives the exact generation commands, requirements, and the external files some scripts read (an Arial font file, and the background images for `list_colours`/`list_shapes`, neither of which is included). A changelog entry is added.
Each script was run over its full range of difficulty levels. All 30 produce `data.json` records with the same fields and types as the released files, the same file naming, and images of the same mode and dimensions.
