Add test and comment

Author: franz1981

core/src/main/java/io/netty/loom/EventLoopScheduler.java

@@ -38,6 +38,7 @@ public record SchedulerContext(long vThreadId, SchedulerRef scheduler) {
          */
         @Override
         public SchedulerRef scheduler() {
+            // TODO consider returning EMPTY_SCHEDULER_REF instead of null
             return (Thread.currentThread().threadId() == vThreadId) ? scheduler : null;
         }
     }

core/src/test/java/io/netty/loom/VirtualMultithreadIoEventLoopGroupTest.java

@@ -349,6 +349,24 @@ void schedulerIsInheritedByForkedVTFromTheRightFactory() throws InterruptedExcep
         }
     }
 
+    @Test
+    void schedulerIsNotInheritedByForkedVT() throws InterruptedException, ExecutionException {
+        try (var group = new VirtualMultithreadIoEventLoopGroup(1, LocalIoHandler.newFactory())) {
+            final var vThreadFactory = group.submit(group::vThreadFactory).get();
+            var schedulerRef = new CompletableFuture<EventLoopScheduler.SchedulerRef>();
+            vThreadFactory.newThread(() -> {
+                try (var scope = StructuredTaskScope.open(allSuccessfulOrThrow())) {
+                    var task = scope.fork(() -> EventLoopScheduler.currentThreadSchedulerContext().scheduler());
+                    scope.join();
+                    schedulerRef.complete(task.get());
+                } catch (InterruptedException e) {
+                    schedulerRef.completeExceptionally(e);
+                }
+            }).start();
+            assertNull(schedulerRef.get());
+        }
+    }
+
    @Test
    void eventLoopSchedulerCanMakeProgressIfTheEventLoopIsBlocked() throws BrokenBarrierException, InterruptedException, TimeoutException {
       var group = new VirtualMultithreadIoEventLoopGroup(1, NioIoHandler.newFactory());