[AbstractWorkStealingScheduler] assert in runtime system in pushBottom

emper/strategies/AbstractWorkStealingScheduler.cpp

@@ -292,6 +292,8 @@ auto AbstractWorkStealingScheduler::nextFiberResultFromMpscQueueOrWorkStealing()
 }
 
 auto AbstractWorkStealingScheduler::pushBottom(AbstractFiber& fiber) -> bool {
+	emper::assertInRuntime();
+
 	auto pushed = queue.pushBottom(&fiber);
 	if (pushed) [[likely]] {
 		onNewWork<CallerEnvironment::EMPER>(emper::FiberHint{emper::FiberSource::local});