Move prepared-file work into app runtime

src/app_runtime.h

@@ -34,6 +34,9 @@ struct AppTask : public std::packaged_task<void()>
 class AppRuntime
 {
 public:
+    AppRuntime();
+    ~AppRuntime();
+
     [[nodiscard]] bool is_render_thread() const noexcept;
     [[nodiscard]] bool is_ui_thread() const noexcept;
     [[nodiscard]] bool request_redraw() const noexcept { return request_redraw_; }
@@ -41,6 +44,7 @@ public:
 
     void notify_render_worker() noexcept;
     void notify_ui_worker() noexcept;
+    void prepared_file_task(std::function<void()> task);
 
     void render_thread_tick(App& app);
     void render_thread_main(App& app, std::stop_token stop_token);
@@ -199,6 +203,15 @@ public:
     }
 
 private:
+    void prepared_file_worker_main(std::stop_token stop_token);
+    void prepared_file_worker_stop();
+
+    std::deque<std::function<void()>> prepared_file_tasklist_;
+    std::mutex prepared_file_task_mutex_;
+    std::condition_variable prepared_file_cv_;
+    std::jthread prepared_file_worker_;
+    bool prepared_file_running_ = true;
+
     std::deque<AppTask> render_tasklist_;
     std::mutex render_task_mutex_;
     std::condition_variable render_cv_;