[targets.*] reworked: artifact is now an inline table with a type discriminator
({type="single-file",filepath} / {type="file-tree",root,outputs}) and steps is an
ordered array-of-tables ({type="typst-compile",template} / {type="shell",run}).
numbering removed entirely (presentation lives in the template per ADR-0011).
TargetConfig { name, artifact: Artifact, steps: Vec<Step> }; Artifact and Step
mirror Spec.Courseware.Artifact / Spec.Courseware.Step (doc-cited). Sensible
defaults so a bare [targets.student] still works: single-file build/<name>.pdf +
one typst-compile exports/<name>.typ. Malformed artifact/step type → non-fatal
SchemaViolation with fallback. 8 tests green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
manifest.toml [targets.*] upgraded from bare names to structured build configs.
Lesson.targets: Vec<String> → Vec<TargetConfig> { name, artifact, numbering }.
ArtifactKind { SingleFile, FileTree } mirrors Spec.Courseware.Artifact.
NumberingConfig.heading: Option<Vec<String>> — None means "use framework
default" (render package owns it), so absence is distinguishable from a value.
Empty [targets.x] body = all defaults, no diagnostics. Malformed config (bad
artifact value, non-array numbering.heading) → non-fatal SchemaViolation, target
kept with defaults. Enabled toml `preserve_order` so target declaration order is
real (the old Vec<String> never actually preserved order). target_names() helper
for call sites that only want names. 8 tests green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>