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.

README.md

@@ -10,14 +10,14 @@ superpaper/                 this repo (orchestration)
 ├── SKILL.md                document-layer skill
 ├── superfig/               submodule — architecture / pipeline / flow
 ├── supertensor/            submodule — tensor faces / axes / shards
-└── superderive/            later — stepwise rewrite figures
+└── superderive/            submodule — stepwise rewrite figures
 ```
 
 | 子仓库 | 画什么 | 远程 |
 |---|---|---|
 | [`superfig`](superfig/) | 节点、边、分组、机制框图 | `carrydela/SuperFig` |
 | [`supertensor`](supertensor/) | 形状对齐的张量公式图 | `carrydela/SuperTensor` |
-| `superderive` | 逐步代数改写图 | 尚未建 |
+| [`superderive`](superderive/) | 逐步代数改写图 | `carrydela/SuperDerive` |
 
 ## Clone
 
@@ -41,13 +41,14 @@ symlinks into this repo:
 skills/superpaper/           SuperPaper
 skills/superfig           -> superpaper/superfig
 skills/supertensor        -> superpaper/supertensor
+skills/superderive        -> superpaper/superderive
 ```
 
 ## Status
 
-v1 notes scaffold is in this repo: ledger schema, router, lint, ingest,
-and three `--work` examples (`excerpt-toy`, `pipeline-delegate`,
-`tensor-delegate`). `superderive` is still phase 2.
+v1 notes scaffold plus v2 `superderive` (phase default 2). Examples:
+`excerpt-toy` (`align`), `pipeline-delegate`, `tensor-delegate`,
+`derive-delegate`.
 
 ```bash
 python3 -m venv .venv && .venv/bin/pip install -r requirements.txt