TranslationScaffold owns the rows that join a translation to the chapters it is
a translation of. Pure refactor: the same events go out in the same order,
`TranslationBatchProposalJvmTest` passes unedited apart from the call it makes,
and no screen behaves differently.
The move is worth making before anything is built on it. A translation chapter
carries no words -- it is `(translation, chapter, position)` and nothing else,
and it exists so a translated chunk has somewhere to hang. Both of the things
it joins arrive on their own schedule: a chapter is signed into an artifact
that already has translations, a translation is started on an artifact that
already has chapters. So the same cross product has to be built from either
side, and a second copy of it is a second chance to disagree about what a
translation covers -- a disagreement that shows up as a chapter nobody can
translate rather than as anything that looks like a bug.
**Over ids, not rows.** `chaptersOf` takes translation ids and a
`SourceChapter`, which is a chapter reduced to which one and where it sits,
rather than a `MantraChapter`. Neither end is always a row: a translation being
proposed exists only as the unsigned event a session is about to sign, and so
does a chapter. `SourceChapter.of` is there for the callers that do hold a row.
**Two things it decides rather than leaves to a caller.** Item order is apply
order, so the nesting is fixed here -- translations outer, chapters inner, which
keeps one translation's chapters contiguous and in reading order. And
`createdAt` is taken once rather than read per template, so a scaffolding
proposed as one act reads as one rather than as events that happen to share a
minute.
The index is the source chapter's own, never the position in the list handed
in. They agree when the list is a whole version in order and stop agreeing the
moment a caller holds a subset, and only one of them is what the group signed.
**Tests.** TranslationScaffoldTest covers it as the pure function it is: the
nesting, both directions it is built from, one timestamp for the lot, the empty
cases, and the index surviving a non-contiguous subset. Checked against a broken
implementation -- taking the index from the list position passes every test that
uses a whole version in order, and is caught by the subset.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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