Add FindByNameRequired throwing variant (yak: Add FindByName! throwing variant)

src/Before.Console/Program.cs

@@ -42,7 +42,7 @@ foreach (var client in DbBase.Context!.Tracked.OfType<Client>())
 }
 
 // ----- find by name -------------------------------------------------------
-Console.WriteLine("\n=== Find by Name ===");
+Console.WriteLine("\n=== Find by Name (null-returning) ===");
 // No context argument: FindByName falls back to the DbBase.Context singleton.
 // This is the ActiveRecord ergonomic — call sites don't carry the context,
 // but the null that comes back on a miss can't tell "no such client" from
@@ -57,3 +57,30 @@ else
 {
     Console.WriteLine("Not found.");
 }
+
+// ----- find by name (throwing variant) ------------------------------------
+Console.WriteLine("\n=== Find by Name Required (throws instead of returning null) ===");
+try
+{
+    var required = Client.FindByNameRequired("Jane Doe");
+    Console.WriteLine($"Found: {required.Name} [{required.Id}]");
+    Console.WriteLine($"  Orders: {required.Orders.Count}");
+}
+catch (InvalidOperationException ex)
+{
+    Console.WriteLine($"Not found: {ex.Message}");
+}
+
+// Show the contrast with a non-existent name:
+Console.WriteLine("\n=== Miss: null-returning vs throwing ===");
+var missNull = Client.FindByName("Nobody Here");
+Console.WriteLine($"FindByName(\"Nobody Here\"): {(missNull == null ? "null" : missNull.Name)}");
+try
+{
+    Client.FindByNameRequired("Nobody Here");
+}
+catch (InvalidOperationException ex)
+{
+    var msg = ex.Message.ReplaceLineEndings(" ").Trim();
+    Console.WriteLine($"FindByNameRequired(\"Nobody Here\"): throws - {msg}");
+}