feat: make SuperPaper the family parent of superfig and supertensor

House the two figure toolkits as git submodules under SuperPaper.
The parent owns paper-note orchestration; children keep their own
history, macros, and lint. DESIGN.md is the family contract.

agents/openai.yaml

@@ -0,0 +1,8 @@
+interface:
+  display_name: "Superpaper"
+  short_description: "把论文编成带 ledger 与路由出图的中文讲义"
+  default_prompt: >-
+    Use $superpaper to reconstruct this paper's argument thread,
+    expand the key derivations, and produce structured Chinese notes.
+    Build ledger.yaml first. Route figures to superfig / supertensor / align;
+    do not draw inside superpaper and do not \usepackage{superfig} in the notes.