One rich scene model {anchor, scenes:[{index,raw,keys,effect}]} that every
consumer will derive from — editing (raw), preview (raw->expanded),
attribution (keys), reset (pool = union of keys), generation. Built on the
existing shortcut-aware verbatim splitter + refinement_keys_in_text, so it
can't disagree with itself. Nothing repointed yet; consumers still on their
own splitters until the staged repointing.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
