improve main.cc readability

common/thread.hh

@@ -25,7 +25,6 @@ class Thread final : public nf7::Context,
   Thread(nf7::Env& env, nf7::File::Id id, Runner&& runner) noexcept :
       nf7::Context(env, id), env_(&env), runner_(std::move(runner)) {
   }
-  virtual ~Thread() noexcept = default;
   Thread(const Thread&) = delete;
   Thread(Thread&&) = delete;
   Thread& operator=(const Thread&) = delete;

common/timed_queue.hh

@@ -89,12 +89,12 @@ class TimedWaitQueue final : private TimedQueue<T> {
   void Notify() noexcept {
     cv_.notify_all();
   }
-  void Wait() noexcept {
+  void Wait(const auto& dur) noexcept {
     std::unique_lock<std::mutex> k(mtx_);
     if (auto t = next_()) {
       cv_.wait_until(k, *t);
     } else {
-      cv_.wait(k);
+      cv_.wait_for(k, dur);
     }
   }