ADR-0087 exemption (no-migration-prescription): No key of any schema is added, removed, renamed or re-shaped, and no export or type changes. The narrowed face is the existing owner-stamp judge now reaching one more collection of a `packages[]` stack's top level: a residual dataset wearing another package's `_packageId`. No conversion can rewrite it, because which package owns the dataset is the author's decision (drop the stamp, or move the dataset into the `packages[]` entry of its owner), and the stack that carries it used to lose the dataset at boot anyway, so there is no working stored state for a migration to preserve.