diagram-design: editorial-style diagram skill for coding agents

The skill supports 45 diagram types, each in minimal light, minimal dark, and full-editorial static variants, output as a self-contained HTML file with inline SVG that opens by double-click, with no build step, JavaScript, or external images. Install via npx skills add cathrynlavery/diagram-design or the plugin-marketplace commands for Claude Code, Codex, GitHub Copilot, and Factory Droid; the cross-agent skills CLI installs the whole skill (references/, assets/, scripts/) into the chosen host directory, symlinking when multiple directories are used so one update syncs all roots. For developers writing blogs or technical docs with Claude Code, Cursor, GitHub Copilot, and similar agents, this means skipping half an hour in Figma for one architecture diagram: describe it in a sentence and the agent picks the type, explains the layout, and writes the HTML file, while an onboard step can pull site colors and fonts for brand consistency. Limits are clear: output quality depends on the model, two runs of the same prompt may lay out differently; the result is a non-editable source format with nothing to diff in a PR and no boxes to drag on a canvas. The docs themselves say Mermaid remains the better choice for Git docs that change every iteration; Diagram Design targets the diagram you're ready to ship.