feat: add superderive child and open phase-2 routing

Attach the stepwise derivation toolkit as a submodule and default
SUPERPAPER_PHASE to 2 so rewrite-figure can use superderive. Notes
still keep align for short expansions without cancel or subst.

scripts/test.sh

@@ -42,7 +42,6 @@ for spec in \
   "align-has-include.yaml:SP014" \
   "included-null-include.yaml:SP015" \
   "screenshot-bad-include.yaml:SP016" \
-  "superderive-v1.yaml:SP022" \
   "retired-reuse.yaml:SP023" \
   "dangling-claim.yaml:SP024"
 do
@@ -73,7 +72,8 @@ for dir in \
   "$ROOT/tests/notes-smoke" \
   "$ROOT/examples/excerpt-toy" \
   "$ROOT/examples/pipeline-delegate" \
-  "$ROOT/examples/tensor-delegate"
+  "$ROOT/examples/tensor-delegate" \
+  "$ROOT/examples/derive-delegate"
 do
   name="$(basename "$dir")"
   if "$ROOT/scripts/build.sh" --work "$dir" >/dev/null 2>&1; then