Implemented phase 6 for the POC prototype in the Website service.

Services/Website/Tests/Library/Cases/Public/Controllers/TradeControllerTests.swift

@@ -141,7 +141,11 @@ struct TradeControllerTests {
 
             // The copy is off sale, for everyone.
             try await client.execute(uri: listing, method: .get) { response in
-                #expect(String(buffer: response.body).contains("This copy is sold."))
+                let body = String(buffer: response.body)
+
+                #expect(body.contains("This copy sold on "))
+                // Three other copies of Nightward #1 remain listed, none of them in this shop.
+                #expect(body.contains("has 0 more copies of Nightward #1, and 3 are listed across CCN."))
             }
 
             // A step out of turn changes nothing.