identity read-back: FromOrderData/FromClientData + DbContext.LoadOrder/LoadClient

Plain field-copy materialization so the persistence round-trip closes.
When OrderLines arrive, FromOrderData becomes the one-line reconstruction
(row description + total become a single line) — the hinge Exercise 2
pivots on.

yak: orderdata-read-back-identity-version-j9ew [order-data-mapping]

tests/BeforeAfter.Tests/AfterPersistenceTests.cs

@@ -88,4 +88,61 @@ public class AfterPersistenceTests
         Assert.Equal(order.Id, found!.Id);
         Assert.Null(db.Find<OrderData>(row => row.Description == "no such order"));
     }
+
+    // ---------------------------------------------------------------------
+    // Read-back: LoadOrder / LoadClient reassemble domain objects from the
+    // stored rows (identity round-trip for now — OrderLines come later).
+    // ---------------------------------------------------------------------
+
+    [Fact]
+    public void Loading_an_order_restores_its_state_and_its_client()
+    {
+        var db = new DbContext();
+        var client = new Client { Name = "Acme" };
+        var order = new Order { Description = "one", TotalInCents = 150_00 };
+        client.Orders.Add(order);
+        db.Save(client);
+        db.Save(order);
+
+        var loaded = db.LoadOrder(order.Id);
+
+        Assert.NotNull(loaded);
+        Assert.Equal(order.Id, loaded!.Id);
+        Assert.Equal("one", loaded.Description);
+        Assert.Equal(150_00, loaded.TotalInCents);
+
+        // The graph is reassembled: the loaded order knows its client again,
+        // and the client's collection holds the loaded order.
+        Assert.NotNull(loaded.Client);
+        Assert.Equal("Acme", loaded.Client!.Name);
+        Assert.Same(loaded, Assert.Single(loaded.Client.Orders));
+    }
+
+    [Fact]
+    public void Loading_a_client_restores_it_with_all_of_its_orders()
+    {
+        var db = new DbContext();
+        var client = new Client { Name = "Acme" };
+        client.Orders.Add(new Order { Description = "one", TotalInCents = 150_00 });
+        client.Orders.Add(new Order { Description = "two", TotalInCents = 250_00 });
+        db.Save(client);
+        db.Save(client.Orders[0]);
+        db.Save(client.Orders[1]);
+
+        var loaded = db.LoadClient(client.Id);
+
+        Assert.NotNull(loaded);
+        Assert.Equal("Acme", loaded!.Name);
+        Assert.Equal(2, loaded.Orders.Count);
+        Assert.All(loaded.Orders, o => Assert.Same(loaded, o.Client));
+    }
+
+    [Fact]
+    public void Loading_an_unknown_id_returns_null()
+    {
+        var db = new DbContext();
+
+        Assert.Null(db.LoadOrder(Guid.NewGuid()));
+        Assert.Null(db.LoadClient(Guid.NewGuid()));
+    }
 }