Load the chosen save slot on selection, fix transition finished re-firing

Picking a save slot now sets SAVE.slotCurrent and calls saveLoadSlot()
before entering the overworld, same slotCurrent/saveSlotInit/saveLoadSlot
sequence saveLoadAllSlots uses per-slot; a load failure shows the fatal
error overlay instead of proceeding with stale/garbage slot data.

Also fixes uiTransitionUpdate firing its "finished" callback every frame
after a transition completes instead of once - latent since the generic
transition system had no real caller yet.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/dusk/ui/screen/mainmenu/uimainmenu.c

@@ -15,9 +15,11 @@
 #include "locale/localemanager.h"
 #include "asset/loader/locale/assetlocaleloader.h"
 #include "ui/dialog/save/uiselectsave.h"
+#include "ui/overlay/uifatalerror.h"
 #include "rpg/cutscene/cutscenesystem.h"
 #include "scene/scene.h"
 #include "asset/asset.h"
+#include "save/save.h"
 
 #define UI_MAIN_MENU_INDEX_START_GAME 0
 #define UI_MAIN_MENU_INDEX_OPTIONS 1
@@ -47,7 +49,15 @@ void uiMainMenuSelectSaveResult(const uint8_t slotIndex, void *user) {
     return;
   }
 
-  // TODO: load/start the game using the chosen save slot.
+  SAVE.slotCurrent = slotIndex;
+  saveSlotInit(&SAVE.slot);
+  errorret_t result = saveLoadSlot();
+  if(errorIsNotOk(result)) {
+    errorCatch(errorPrint(result));
+    uiFatalErrorOpen(result.state->message);
+    return;
+  }
+
   sceneSet(SCENE_TYPE_OVERWORLD);
 }
 

src/dusk/ui/transition/uitransition.c

@@ -54,7 +54,15 @@ errorret_t uiTransitionUpdate(void) {
   );
 
   if(UI_TRANSITION.data.t >= 1.0f && UI_TRANSITION.finished) {
-    UI_TRANSITION.finished(UI_TRANSITION.user);
+    // Saved and cleared before firing so a callback that immediately
+    // starts another transition isn't clobbered by this function's own
+    // cleanup running after it - same reentrancy hazard as uiFocusPop,
+    // see src/dusk/ui/focus/uifocus.c. Without this, finished would also
+    // just keep re-firing every frame forever once t reaches 1.0.
+    uitransitioncallback_t finished = UI_TRANSITION.finished;
+    void *user = UI_TRANSITION.user;
+    UI_TRANSITION.finished = NULL;
+    finished(user);
   }
 
   errorOk();