fix(reef): omit absent receipt categories from audit state (#110177)

extensions/reef/protocol/audit-receipts.test.ts

@@ -140,6 +140,8 @@ describe("receipts", () => {
       "accepted",
       "rejected",
     ]);
+    expect(entries[0]!.event.payload).not.toHaveProperty("category");
+    expect(entries[1]!.event.payload).toHaveProperty("category", "guard_deny");
     await expect(
       confirmDelivery({ ...accepted, bodyHash: "e".repeat(64) }, identity.signing.publicKey, audit),
     ).rejects.toThrow("invalid delivery receipt");

extensions/reef/protocol/receipts.ts

@@ -61,7 +61,7 @@ export async function confirmDelivery(
   return appendAudit(audit, "confirm_delivery", {
     receipt,
     status: receipt.status,
-    category: receipt.category,
+    ...(receipt.category ? { category: receipt.category } : {}),
   });
 }