Standalone TikZ to PNG with tectonic and pixi

For blog posts and slides I normally embed Graphviz DOT directly in orgmode and let the export handle rendering. That works well until a paper schematic needs inline math or a font family that does not cover enough Unicode glyphs 1 . At that point, TikZ in a standalone document class is the path of least resistance: full LaTeX math rendering, arbitrary fonts through the TeX ecosystem, and tightly…