fix(deliveries): reader must not invent lines on rotated or cluttered photos

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/dn-pipeline/extract.ts

@@ -134,6 +134,15 @@ Rules:
   or "Reg No" block (weighbridge tickets) names the lorry company, never the
   supplier. A Raumix, Drift or similar ticket stays that quarry's even when a
   haulier such as Herlendir or HC Sand is printed lower down.
+- Photos may be rotated, sideways, upside down, blurred or taken on top of a
+  site drawing or map. Turn the paper the right way round in your head and read
+  only the slip itself; the drawing underneath is never part of the document.
+  Every item line, quantity, rate, date and number must be something you can
+  actually see printed or handwritten on the slip. If you cannot read a field
+  return null (and receiving_status unreadable for a quantity); if you cannot
+  read the item table at all return an empty items array and describe what you
+  see in raw_text. Never invent plausible lines, products, rates or numbers,
+  and never use a different slip's content as a guess.
 - po_number_raw: the customer order number exactly as printed (ours look like
   MEGCPO9476). Copy every letter and digit; never drop, add or swap a digit.
 - doc_number: the reference appropriate to that type - the delivery note