Publish Substack Article

This automates publishing Markdown articles to Substack by converting them to HTML and pasting into the editor as rich text. It handles the full workflow: extracts titles from frontmatter or headers, converts Markdown with proper code blocks and formatting, uses clipboard paste to preserve styling (direct fill would strip formatting), and saves everything as a draft. One notable quirk: Substack's editor doesn't support HTML tables, so it includes a preprocessing step to convert tables to PNG images via the diagram-to-image skill before uploading. Works with both Playwright and Chrome DevTools MCP servers, defaulting to Playwright. Useful if you write in Markdown but need Substack's rich editor for final review and publishing.