fix circular module dep: thread trackID counter via pointer instead of include

G4tracking cannot include G4EventManager.hh because G4event already
depends on G4tracking, creating a circular dependency. Fix: pass a
raw G4int* pointer to the event-level trackIDCounter from G4EventManager
through G4TrackingManager::SetTrackIDCounter into G4SteppingManager,
where ProcessSecondariesFromParticleChange uses it to pre-assign track
IDs without any new include.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

source/event/include/G4EventManager.hh

@@ -59,9 +59,6 @@ class G4EventManager
     static G4EventManager* GetEventManager();
       // This method returns the singleton pointer of G4EventManager.
 
-    G4int ReserveNextTrackID();
-      // Pre-assign the next sequential track ID to a secondary being born inside
-      // G4SteppingManager, so that its ID is available in UserSteppingAction.
 
     G4EventManager();
    ~G4EventManager();

source/event/src/G4EventManager.cc

@@ -172,6 +172,8 @@ void G4EventManager::DoProcessing(G4Event* anEvent,
   }
 #endif
 
+  trackManager->SetTrackIDCounter(&trackIDCounter);
+
   std::unordered_set<G4VTrackingManager *> trackingManagersToFlush;
 
   do
@@ -401,11 +403,6 @@ G4int G4EventManager::StoreSubEvent(G4Event* evt, G4int& subEvtType, G4SubEvent*
   return evt->StoreSubEvent(subEvtType,se);
 }
 
-G4int G4EventManager::ReserveNextTrackID()
-{
-  return ++trackIDCounter;
-}
-
 void G4EventManager::StackTracks(G4TrackVector* trackVector,
                                  G4bool IDhasAlreadySet)
 {