Function layout_migration_to_json 

pub fn layout_migration_to_json(result: &LayoutMigrationResult) -> Value

What migrateLayout() answers with, in the shape of the TS LayoutMigrationResult. Every path crosses as the engine spelled it, which on the WASM binding is a path inside the module’s preopened namespace — the shim rewrites those into host paths, as it already does for a refusal.