Replace a supported ordinary product or uniquely owned single-flight stair.
Other product classes and non-stair aggregate roots refuse before preparation.
A builder/anchor/ownership refusal preserves the original graph, journal and
allocator. Shared shape/style leaves are retained, as with generic removal.
Anchor preparation may write into this same draft without nesting a transaction.
Replace a supported ordinary product or uniquely owned single-flight stair. Other product classes and non-stair aggregate roots refuse before preparation. A builder/anchor/ownership refusal preserves the original graph, journal and allocator. Shared shape/style leaves are retained, as with generic removal. Anchor preparation may write into this same draft without nesting a transaction.