feat(cph): implement nested outline manifest and batch/combined export

ADR-0029 — nested outline manifest, supersedes ADR-0008's flat [[parts]]:
- cph-model: recursive loader over manifest.toml containers / element.toml
  leaves; Lesson.parts (pure elements, DFS order) + Lesson.outline (elements
  interleaved with section headings at their DFS-open position); rejects
  ambiguous/incomplete folders and root-vs-container table misplacement
- cph-diag: new DiagCode::ManifestMalformed for carrier-document structure
  errors (discharges an existing TODO)
- cph-typst: augmented manifest now serializes the outline (element/section
  entries) instead of a flat parts array
- render/lib.typ: render-lesson renders section headings at their depth
- examples/TH-141 migrated to 5 nested section containers + 3 root segments,
  byte-identical element order; smoke-verified via cph check/build + pdftotext

ADR-0030 — batch & combined export, extends ADR-0009/0011:
- cph build with no --target batches every declared target (repeatable
  --target for an explicit subset); any target failure => non-zero exit,
  per-target ledger, independent per-target execution
- cph-model: bundle.toml loader (directory + [info]/[targets.*]/ordered
  lessons with per-lesson target overrides)
- cph-typst: augmented bundle manifest (path-prefixed member outlines),
  Engine::{compile_check_bundle,build_bundle_pdf}
- render/lib.typ: render-bundle assembles member lessons under per-lesson
  headings, depth-shifts their own section headings, resets example/lemma
  counters at each lesson boundary by default
- cph-cli: `cph bundle <path> --target <name>` subcommand, same batching
  contract as `cph build`
- new bundle fixtures/tests (cph-model unit + cph-typst through-template PDF
  compile), smoke-verified via a real 2-lesson merged PDF

Verification: cargo fmt/clippy/test clean across the workspace (68 tests);
real cph check/build/bundle runs against TH-141 and a bundle fixture, PDF
content inspected via pdftotext.

examples/TH-141/液气界面/lemmas/LJ对势积分标度/element.toml

@@ -0,0 +1 @@
+kind = "lemma"

examples/TH-141/液气界面/lemmas/LJ对势积分标度/proof.typ

@@ -0,0 +1,13 @@
+设下半空间体相分子的数密度为 $n_v = 1 \/ d^3$。固定一个表面分子作为参考分子，对其与下半空间所有体相分子的相互作用求和。由对称性，相对参考分子距离 $r$ 在下半空间内的体积元为 $dif V = 2 pi r^2 dif r$。下限取 $r = d$，上限取 $infinity$：
+
+$ Delta U = 2 pi n_v integral_d^infinity u(r) thin r^2 dif r . $
+
+代入 $u(r)$，用 $integral r^2 dot r^(-n) dif r = r^(3 - n) \/ (3 - n)$ 化简，得
+
+$ Delta U tilde.op epsilon . $
+
+把 $Delta U$ 乘以单位面积分子数 $n_s tilde.op 1 \/ d^2$，由 @骨架公式 即得
+
+$ sigma tilde.op epsilon / d^2 , $
+
+即 @LJ标度。

examples/TH-141/液气界面/lemmas/LJ对势积分标度/stmt.typ

@@ -0,0 +1,9 @@
+设分子间对势为 Lennard–Jones 6-12 形式
+
+$ u(r) = 4 epsilon [(d \/ r)^(12) - (d \/ r)^6] . $
+
+把一个表面分子与下半空间所有分子的相互作用积分求和，得到
+
+$ sigma tilde.op epsilon / d^2 . $ <LJ标度>
+
+此式与量纲估计 @量纲估计 同标度。