feat: land superpaper v1 notes scaffold

Add the ledger schema, class router, lint codes, ingest/build
pipeline, and three work-tree examples: align derivation,
superfig delegation, and supertensor delegation.

references/checklist.md

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+# Delivery checklist
+
+- Ledger written first; every core claim has `\splabel`.
+- Formula three-beat present wherever display math appears.
+- Each figure toolkit matches `scripts/router.py`; mixed-class rows were split.
+- Notes do not `\usepackage{superfig|supertensor|superderive}`.
+- Vector figures are PDF includes; screenshots are `orig.png` with a source footnote.
+- `scripts/lint.py --work` and `scripts/build.sh --work` are green.
+- Overfull in the notes log is allowed; missing glyphs and undefined refs are not.