feat: add superfig paper-figure toolkit

Standalone LaTeX/TikZ skill for non-tensor paper figures: node/edge
macros, lint-on-warning build, golden examples, and negative fixtures.

tests/smoke.tex

@@ -0,0 +1,27 @@
+% English-label smoke: cursor row, operator, meaning box, formula last.
+\documentclass[border=8pt]{standalone}
+\usepackage[en]{superfig}
+
+\sfsetrole{x}{sfTeal}
+\sfsetrole{y}{sfOrange}
+
+\begin{document}
+\begin{tikzpicture}
+\sfstage{S}{one band}
+\sfrow{R1}{12mm}
+  \sfnode[role=x]{A}{$A$}{14mm}{10mm}
+  \sfop{op}{$\circ$}
+  \sfnode[role=y]{B}{$B$}{14mm}{10mm}
+\sfrowend
+\sflane{R1}
+\sfcaption{A}{$A$}{left}
+\sfcaption{B}{$B$}{right}
+\sfbbox{all}
+\sftopformula{F}{$B = A \circ f$}
+\sfmeaningbox{mb}{92mm}{all}
+  {one composition}
+  {two objects}
+  {the operator sits in the flow and reserves its own width}
+\sfsignature{Smoke test}{mb}
+\end{tikzpicture}
+\end{document}