docs: fix stale @doNotGenerate inheritance example (#5002)

docs/06-concepts/01-working-with-endpoints/02-endpoint-inheritance.md

@@ -108,12 +108,34 @@ This way, you can modify the behavior of endpoint methods while still sharing th
 
 ## Hiding endpoint methods with `@doNotGenerate`
 
-In case you want to hide methods from an endpoint use `@doNotGenerate` in the child class like so:
+In case you want to hide a method that the child class declares itself (i.e. one that is not inherited from a parent class whose client is still being generated), annotate it with `@doNotGenerate` like so:
 
 ```dart
 import 'package:serverpod/serverpod.dart';
 
-abstract class CalculatorEndpoint extends Endpoint {
+class AdderEndpoint extends Endpoint {
+  Future<int> add(Session session, int a, int b) async {
+    return a + b;
+  }
+
+  @doNotGenerate
+  Future<int> subtract(Session session, int a, int b) async {
+    throw UnimplementedError();
+  }
+}
+```
+
+`AdderEndpoint` exposes `add`, but `subtract` is annotated with `@doNotGenerate` and is therefore excluded from the generated client.
+
+### Hiding an inherited method
+
+Hiding a method that is *inherited* from a parent class only works if the parent class itself is fully annotated with `@doNotGenerate`, meaning no client class is generated for it at all:
+
+```dart
+import 'package:serverpod/serverpod.dart';
+
+@doNotGenerate
+class CalculatorEndpoint extends Endpoint {
   Future<int> add(Session session, int a, int b) async {
     return a + b;
   }
@@ -125,16 +147,21 @@ abstract class CalculatorEndpoint extends Endpoint {
 
 class AdderEndpoint extends CalculatorEndpoint {
   @doNotGenerate
+  @override
   Future<int> subtract(Session session, int a, int b) async {
     throw UnimplementedError();
   }
 }
 ```
 
-Since `CalculatorEndpoint` is `abstract`, it will not be exposed on the server. `AdderEndpoint` inherits all methods from its parent class, but since it opts to hide `subtract` by annotating it with `@doNotGenerate` only the `add` method will be exposed.
+Since `CalculatorEndpoint` is annotated with `@doNotGenerate`, it will not be exposed on the server, and no client class is generated for it. `AdderEndpoint` inlines the inherited methods directly, and since it re-declares `subtract` with `@doNotGenerate`, only `add` is exposed on the generated client.
 Don't worry about the exception in the `subtract` implementation. That is only added to satisfy the Dart compiler – in practice, nothing will ever call this method on `AdderEndpoint`.
 
-Hiding endpoints from a super class is only appropriate in case the parent `class` is `abstract` or annotated with `@doNotGenerate`. Otherwise, the method that should be hidden on the child would still be accessible via the parent class.
+:::warning
+If the parent class is only `abstract` (and not itself annotated with `@doNotGenerate`), Serverpod still generates an abstract client class that mirrors it, and every subclass's generated client must implement all of its methods. In that case, `@doNotGenerate` **cannot** be used to hide an inherited method – doing so removes the method from the subclass's generated client while the abstract client class still declares it, which causes a Dart compile error ("missing concrete implementation"). To hide an inherited method, the parent class must be marked `@doNotGenerate` itself, not just `abstract`.
+
+If the parent class is a normal, concrete class (neither `abstract` nor `@doNotGenerate`), it is exposed on the server and the client in its own right. Hiding the method on the child only removes it from the child's client – it remains accessible through the parent's own generated client class.
+:::
 
 ## Unhiding endpoint methods annotated with `@doNotGenerate` in the super class