feat(examples): migrate TH-141 sample to declarative layout (WU-6)

Real-content fixture for the end-to-end pipeline. TH-141 (39 parts: 22 segment,
15 lemma, 2 example) migrated from the prototype's typst `#let parts` manifest
to ADR-0008: declarative manifest.toml (project+info+ordered parts+targets) +
per-element element.toml (kind + scalars; examples carry `source`). Content .typ
files copied byte-identical (no math corruption); per-element main.typ + meta.toml
dropped (wiring is now generated). Part order matches source exactly; 5 lemmas
have no proof.typ (optional); no cross-file imports / paralearn refs / figs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

examples/TH-141/manifest.toml

@@ -0,0 +1,166 @@
+[project]
+id   = "local-mpttwr3t-sn1oma"
+name = "TH-141_表面张力的严肃理论"
+
+[info]
+title  = "TH-141:表面张力的严肃理论"
+author = "范式教育教研组"
+
+[[parts]]
+kind = "segment"
+path = "segments/开场对照导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/胡克唯象模型回顾"
+
+[[parts]]
+kind = "segment"
+path = "segments/液面拉伸的本质"
+
+[[parts]]
+kind = "segment"
+path = "segments/液气界面导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/微观建模的共同骨架"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/量纲分析估计"
+
+[[parts]]
+kind = "segment"
+path = "segments/缺键模型导言"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/缺键模型一般公式"
+
+[[parts]]
+kind = "example"
+path = "examples/41届复赛三-2-缺键模型"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/Stefan极简估算"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/立方格子下zeta具体值"
+
+[[parts]]
+kind = "segment"
+path = "segments/LJ积分导言"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/LJ对势积分标度"
+
+[[parts]]
+kind = "segment"
+path = "segments/固气界面导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/表面能γ与表面应力f"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/拉伸固体的总应力"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/缺键模型迁移到固气"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/固体表面能的晶面各向异性"
+
+[[parts]]
+kind = "segment"
+path = "segments/不同物质γ量级对比"
+
+[[parts]]
+kind = "segment"
+path = "segments/固液界面导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/固液界面能的物理图像"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/Dupré关系"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/Girifalco-Good公式"
+
+[[parts]]
+kind = "segment"
+path = "segments/Fowkes极性修正"
+
+[[parts]]
+kind = "segment"
+path = "segments/三相接触导言"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/Young方程"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/GGZ浸润判据"
+
+[[parts]]
+kind = "segment"
+path = "segments/浸润全谱与高低能表面"
+
+[[parts]]
+kind = "segment"
+path = "segments/σT建模导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/微观派Lm下降"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/Eötvös规则"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/Guggenheim-Katayama改良"
+
+[[parts]]
+kind = "lemma"
+path = "lemmas/表面熵热力学关系"
+
+[[parts]]
+kind = "segment"
+path = "segments/σTp态函数导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/σ作为态函数的图像"
+
+[[parts]]
+kind = "example"
+path = "examples/41届复赛三-1-混注石油"
+
+[[parts]]
+kind = "segment"
+path = "segments/收束导言"
+
+[[parts]]
+kind = "segment"
+path = "segments/各模型对水的预测对照"
+
+[[parts]]
+kind = "segment"
+path = "segments/算不准背后的真实物理"
+
+[targets.student]
+[targets.teacher]