feat: gate writer sections on a % teach: block (SP025)

Rewrite references/pedagogy.md around recite-vs-teach: reader model,
coverage density (sections_in is cite permission, not a to-do list),
intuition-before-formula three-beat, and paper-jump filling.

Every notes/sections/sec-*.tex must now answer gap / takeaway / jump /
omit above the first \section. lint.py checks presence only (it cannot
judge honesty); files opening with "% generated by" are exempt.

- scripts/lint.py: SP025 + is_writer_section / teach_gaps helpers
- tests/no-teach-block/: fixture with takeaway only, wired into test.sh
- examples/*: all 14 writer sections get real teach blocks
- SKILL.md, references/{agents,antipatterns,checklist}.md, DESIGN.md,
  assets/notes-template.tex: route writers and consistency agent
  through pedagogy.md

SKILL.md

@@ -47,7 +47,7 @@ or when the source is a lecture video.
 1. `./scripts/preflight.sh`。0 = 全路径，1 = 降级（说出口），2 = 无 LaTeX。
 2. `./scripts/ingest.sh --work <dir> …`（`references/input.md`）。
 3. 从 `assets/ledger.example.yaml` 写 `ledger.yaml`，再写 `outline.md`，再写正文。
-4. 公式三拍：中文动机 → `\[` / `align` → 扁平符号表（`references/pedagogy.md`）。
+4. 写正文：教，不要复述（`references/pedagogy.md`）。公式三拍：直觉 → `\[` / `align` → 扁平符号表。
 5. 按 `references/router.md` 填 figure plan。每张重绘图一份 `F*.request.md`，figure agent 只读它和对应子仓库 `SKILL.md`。
 6. `./scripts/lint.py --work <dir>` 然后 `./scripts/build.sh --work <dir>`。
 7. 改术语或改图：先改 ledger，再改那一处。
@@ -59,9 +59,9 @@ Worked trees: `examples/excerpt-toy/`（`align`）、`examples/pipeline-delegate
 ```
 $superpaper <源> 请 spawn 多 sub agents，隔离上下文：
   - 1 个 outline agent：写 ledger.yaml + outline.md + 节边界
-  - N 个 writer agents：各写 sections/sec-XX.tex，引用 ledger id
+  - N 个 writer agents：先读 references/pedagogy.md，各写 sections/sec-XX.tex，引用 ledger id
   - 每个计划重绘图 1 个 figure agent：只读 F*.request.md，调用对应子仓库 skill
-  - 1 个 consistency agent：符号、术语、claim 覆盖、路由一致性
+  - 1 个 consistency agent：符号、术语、claim 覆盖、路由一致性、是否复述（pedagogy.md）
 ```
 
 必须拆 agent 当且仅当：正文 > 12 页，或顶层节 > 4，或重绘图 ≥ 2，或用户显式要求 spawn。