For agents, on top of README.md, which they read first.

Notes for agents

• The SVGs are upstream's, unchanged. Do not recolour, resize or reformat them. To update, copy from a clone of shuqikhor/pixel-icons and change the date in the README.
• site::config::Pic embeds them with include_str!; its test holds the enum to this directory: no file unused, no use without a file. Adding an icon is a new variant and a new file together.
• The LICENSE stays beside the icons, and the page's footer keeps the credit.