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.

examples/excerpt-toy/source/excerpt.md

@@ -0,0 +1,8 @@
+# A One-Step Predictor (fixture)
+
+We predict $\hat y = f_\theta(x)$ in one forward pass. The loss
+$L(\hat y, y)$ is computed after the prediction; it is not a station
+on the forward path.
+
+The scale $1/\sqrt{d}$ is introduced so that the variance of the
+inner product does not grow with $d$.