fix(core): stabilize HTTP/WS runtime lifecycle and improve shutdown handling

- unify App, HTTPServer and Session lifecycle
- improve SIGINT (Ctrl+C) responsiveness
- ensure safe session teardown without blocking threads
- remove unsafe background behaviors in Session
- prepare foundation for executor-driven scheduling

Author: GaspardKirira

include/vix/app/App.hpp

@@ -26,7 +26,7 @@
 #include <vector>
 
 #include <vix/config/Config.hpp>
-#include <vix/executor/IExecutor.hpp>
+#include <vix/executor/RuntimeExecutor.hpp>
 #include <vix/http/RequestHandler.hpp>
 #include <vix/http/ResponseWrapper.hpp>
 #include <vix/router/Router.hpp>
@@ -120,7 +120,7 @@ namespace vix
      *
      * @param executor Shared executor used by the application.
      */
-    explicit App(std::shared_ptr<vix::executor::IExecutor> executor);
+    explicit App(std::shared_ptr<vix::executor::RuntimeExecutor> executor);
 
     /**
      * @brief Destroys the application and releases owned resources.
@@ -318,11 +318,11 @@ namespace vix
     }
 
     /**
-     * @brief Returns the executor used by the application.
+     * @brief Returns the runtime executor used by the application.
      *
-     * @return vix::executor::IExecutor& Executor.
+     * @return vix::executor::RuntimeExecutor& Executor.
      */
-    vix::executor::IExecutor &executor() noexcept
+    vix::executor::RuntimeExecutor &executor() noexcept
     {
       return *executor_;
     }
@@ -1011,7 +1011,7 @@ namespace vix
   private:
     vix::config::Config config_;
     std::shared_ptr<vix::router::Router> router_;
-    std::shared_ptr<vix::executor::IExecutor> executor_;
+    std::shared_ptr<vix::executor::RuntimeExecutor> executor_;
     vix::server::HTTPServer server_;
 
     ShutdownCallback shutdown_cb_{};

include/vix/server/HTTPServer.hpp

@@ -27,7 +27,7 @@
 #include <vix/async/core/task.hpp>
 #include <vix/async/net/tcp.hpp>
 #include <vix/config/Config.hpp>
-#include <vix/executor/IExecutor.hpp>
+#include <vix/executor/RuntimeExecutor.hpp>
 #include <vix/router/Router.hpp>
 
 namespace vix::server
@@ -59,7 +59,6 @@ namespace vix::server
    *
    * This server does not depend on Boost.Asio or Boost.Beast.
    * Networking is provided by vix::async::net and application execution is
-   * delegated through vix::executor::IExecutor.
    */
   class HTTPServer
   {
@@ -74,7 +73,7 @@ namespace vix::server
      */
     explicit HTTPServer(
         vix::config::Config &config,
-        std::shared_ptr<vix::executor::IExecutor> executor);
+        std::shared_ptr<vix::executor::RuntimeExecutor> executor);
 
     HTTPServer(const HTTPServer &) = delete;
     HTTPServer &operator=(const HTTPServer &) = delete;
@@ -196,7 +195,7 @@ namespace vix::server
      *
      * @return Shared executor instance.
      */
-    [[nodiscard]] std::shared_ptr<vix::executor::IExecutor> executor() const noexcept
+    std::shared_ptr<vix::executor::RuntimeExecutor> executor() const noexcept
     {
       return executor_;
     }
@@ -312,7 +311,7 @@ namespace vix::server
     /**
      * @brief Generic executor used for application work.
      */
-    std::shared_ptr<vix::executor::IExecutor> executor_;
+    std::shared_ptr<vix::executor::RuntimeExecutor> executor_;
 
     /**
      * @brief Threads running the native async I/O context.

include/vix/session/Session.hpp

@@ -28,7 +28,7 @@
 #include <vix/async/core/timer.hpp>
 #include <vix/async/net/tcp.hpp>
 #include <vix/config/Config.hpp>
-#include <vix/executor/IExecutor.hpp>
+#include <vix/executor/RuntimeExecutor.hpp>
 #include <vix/http/Request.hpp>
 #include <vix/http/Response.hpp>
 #include <vix/router/Router.hpp>
@@ -77,10 +77,11 @@ namespace vix::session
      * @param config Server configuration.
      * @param executor Executor used for handler execution.
      */
-    explicit Session(std::unique_ptr<tcp_stream> stream,
-                     vix::router::Router &router,
-                     const vix::config::Config &config,
-                     std::shared_ptr<vix::executor::IExecutor> executor);
+    explicit Session(
+        std::unique_ptr<tcp_stream> stream,
+        vix::router::Router &router,
+        const vix::config::Config &config,
+        std::shared_ptr<vix::executor::RuntimeExecutor> executor);
 
     /** @brief Destroy the session. */
     ~Session() = default;
@@ -195,7 +196,7 @@ namespace vix::session
     std::unique_ptr<tcp_stream> stream_;
     vix::router::Router &router_;
     const vix::config::Config &config_;
-    std::shared_ptr<vix::executor::IExecutor> executor_;
+    std::shared_ptr<vix::executor::RuntimeExecutor> executor_;
 
     std::string read_buffer_{};
     std::shared_ptr<io_context> io_context_{};

src/app/App.cpp

@@ -13,7 +13,6 @@
  */
 #include <vix/app/App.hpp>
 
-#include <vix/experimental/ThreadPoolExecutor.hpp>
 #include <vix/openapi/register_docs.hpp>
 #include <vix/router/Router.hpp>
 #include <vix/utils/Env.hpp>
@@ -125,24 +124,13 @@ namespace
     return static_cast<std::size_t>(hc);
   }
 
-  std::shared_ptr<vix::executor::IExecutor> make_default_executor()
+  std::shared_ptr<vix::executor::RuntimeExecutor> make_default_executor()
   {
-    const std::size_t threads = compute_executor_threads();
-    const std::size_t max_threads = threads;
-    constexpr int default_priority = 0;
+    const auto threads = static_cast<std::uint32_t>(compute_executor_threads());
 
-    std::unique_ptr<vix::executor::IExecutor> exec =
-        vix::experimental::make_threadpool_executor(
-            threads,
-            max_threads,
-            default_priority);
-
-    if (!exec)
-    {
-      throw std::runtime_error("failed to create default thread pool executor");
-    }
-
-    return std::shared_ptr<vix::executor::IExecutor>(std::move(exec));
+    auto exec = std::make_shared<vix::executor::RuntimeExecutor>(threads);
+    exec->start();
+    return exec;
   }
 
   void register_bench_route(vix::router::Router &router)
@@ -244,7 +232,7 @@ namespace vix
     }
   }
 
-  App::App(std::shared_ptr<vix::executor::IExecutor> executor)
+  App::App(std::shared_ptr<vix::executor::RuntimeExecutor> executor)
       : config_(),
         router_(nullptr),
         executor_(std::move(executor)),
@@ -255,6 +243,8 @@ namespace vix
       log().throwError("App: executor cannot be null");
     }
 
+    executor_->start();
+
     log().setPattern("[%Y-%m-%d %H:%M:%S.%e] [%^%l%$] %v");
     log().setLevel(parse_log_level_from_env());
 

src/server/HTTPServer.cpp

@@ -75,8 +75,9 @@ namespace vix::server
     }
   } // namespace
 
-  HTTPServer::HTTPServer(vix::config::Config &config,
-                         std::shared_ptr<vix::executor::IExecutor> executor)
+  HTTPServer::HTTPServer(
+      vix::config::Config &config,
+      std::shared_ptr<vix::executor::RuntimeExecutor> executor)
       : config_(config),
         io_context_(std::make_shared<vix::async::core::io_context>()),
         listener_(nullptr),

src/session/Session.cpp

@@ -187,7 +187,7 @@ namespace vix::session
   Session::Session(std::unique_ptr<tcp_stream> stream,
                    vix::router::Router &router,
                    const vix::config::Config &config,
-                   std::shared_ptr<vix::executor::IExecutor> executor)
+                   std::shared_ptr<vix::executor::RuntimeExecutor> executor)
       : stream_(std::move(stream)),
         router_(router),
         config_(config),