test(examples): TH-141 declares structured target build config (WU-E)

Acceptance fixture for the export-as-build model. TH-141's [targets.student] /
[targets.teacher] now carry artifact = "single-file" + an explicit per-level
heading numbering override (一、 / 1.1 / 1.1.1), exercising ADR-0009's
file-resident override path end-to-end.

Verified: `cph check` → 0 errors / 0 warnings; `cph build` both targets → PDFs
(student 9pp, teacher 12pp) with correct numbering — zero "二、一" occurrences
(the bug the override layer was missing to fix). numbly resolves offline through
the embedded engine via the vendored package.

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

examples/TH-141/manifest.toml

@@ -162,5 +162,16 @@ path = "segments/各模型对水的预测对照"
 kind = "segment"
 path = "segments/算不准背后的真实物理"
 
+# Export targets (ADR-0009): each is a build producing a typed artifact, with
+# file-resident presentation config that overrides the framework defaults.
+# Heading numbering is given explicitly per level (level-1 一、, level-2 1.1,
+# level-3 1.1.1) — overriding the render package's default via the in-file path.
 [targets.student]
+artifact = "single-file"
+[targets.student.numbering]
+heading = ["{1:一}、", "{1:1}.{2:1}", "{1:1}.{2:1}.{3:1}"]
+
 [targets.teacher]
+artifact = "single-file"
+[targets.teacher.numbering]
+heading = ["{1:一}、", "{1:1}.{2:1}", "{1:1}.{2:1}.{3:1}"]