validate_structural(order) runs before save_orders_batch insert.
Catches malformed payloads (MISSING_FIELD, INVALID_DATE, EMPTY_ITEMS,
INVALID_QUANTITY, INVALID_PRICE) that would otherwise crash the batch
insert or downstream pipeline. 17 unit tests cover each rule.
Does NOT validate SKU existence — redundant with _dedup_items_by_sku
pass-through and validate_skus Oracle lookup.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
