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/tracking/include/G4SteppingManager.hh

@@ -90,6 +90,7 @@ class G4SteppingManager
   void SetUserAction(G4UserSteppingAction* apAction);
   G4Track* GetTrack() const;
   void SetVerboseLevel(G4int vLevel);
+  void SetTrackIDCounter(G4int* counter) { fTrackIDCounter = counter; }
   void SetVerbose(G4VSteppingVerbose*);
   G4Step* GetStep() const;
   void SetNavigator(G4Navigator* value);
@@ -195,6 +196,8 @@ class G4SteppingManager
 
   G4double sumEnergyChange = 0.0;
 
+  G4int* fTrackIDCounter = nullptr; // pointer into G4EventManager::trackIDCounter, set via SetTrackIDCounter
+
   G4VParticleChange* fParticleChange = nullptr;
   G4Track* fTrack = nullptr;
   G4TrackVector* fSecondary = nullptr;

source/tracking/include/G4TrackingManager.hh

@@ -78,6 +78,7 @@ class G4TrackingManager
   void SetStoreTrajectory(G4int value);
 
   G4SteppingManager* GetSteppingManager() const;
+  void SetTrackIDCounter(G4int* counter) { fpSteppingManager->SetTrackIDCounter(counter); }
 
   G4UserTrackingAction* GetUserTrackingAction() const;