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.

references/fallback.md

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+# Fallback without LaTeX
+
+Use this path only when `scripts/preflight.sh` exits 2. State explicitly that the
+`superfig.sty` guarantees — role registry, cursor layout, package warnings, and the build
+pipeline — are unavailable.
+
+## Preserve manually
+
+1. Build the semantics ledger before drawing.
+2. One hue per role; at most four hues plus gray; three lightness levels.
+3. Every node is one object; every edge has one relationship; groups are real composites.
+4. Derive placement from previous bounding boxes plus one gutter constant, not per-label
+   tuning.
+5. Export SVG and PNG, then inspect full-size and at 360 px using `checklist.md`.
+
+Prefer SVG for editability. Do not imitate package compliance in the delivery: name the
+fallback renderer and list any inferred relationship or reduced guarantee.