Define SW4's behaviour for a market-less quote

Shipped

26 ஆகஸ்ட், 2026 அன்று 6:32 PM UTC

Author

kamo

Commit

dd9095b

Task 1 made create() read marketUid but did not backfill, so every quote that exists today still has a null market. The converter must fall back to PurchaseLineItem rather than throw — throwing would make conversion impossible for every quote currently in the system. Records the related backfill question: revise() copies market forward but reuses the prior engagement, so pre-Task-1 RETAIL stamps propagate.