migrat a SDL3 Callback API (SDL_AppInit/Iterate/Event/Quit) (milestone 3)

- main.cpp reescrit amb SDL_MAIN_USE_CALLBACKS
- Director convertit a màquina d'estats amb iterate() i handleEvent()
- Seccions (Logo, Intro, Title, Game) amb iterate() i handleEvent()
- Events SDL enrutats via SDL_AppEvent → Director → secció activa
- Eliminat SDL_PollEvent de iterate(), events via handleEvent()
- Transicions entre seccions gestionades per handleSectionTransition()
- Instructions i Game (demo) delegats frame a frame des de Title

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

source/main.cpp

@@ -39,15 +39,26 @@ Reescribiendo el código el 27/09/2022
 
 */
 
-#include <memory>
+#define SDL_MAIN_USE_CALLBACKS 1
+#include <SDL3/SDL_main.h>
 
 #include "director.h"
 #include "stb_vorbis.c"
 
-int main(int argc, char *argv[]) {
-    // Crea el objeto Director
-    auto director = std::make_unique<Director>(argc, const_cast<const char **>(argv));
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[]) {
+    auto *director = new Director(argc, const_cast<const char **>(argv));
+    *appstate = director;
+    return SDL_APP_CONTINUE;
+}
 
-    // Bucle principal
-    return director->run();
-}
+SDL_AppResult SDL_AppIterate(void *appstate) {
+    return static_cast<Director *>(appstate)->iterate();
+}
+
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event) {
+    return static_cast<Director *>(appstate)->handleEvent(event);
+}
+
+void SDL_AppQuit(void *appstate, SDL_AppResult result) {
+    delete static_cast<Director *>(appstate);
+}