Clear the previous exit block when entering a daughter

This fixes a stale exit block in the relocating VecGeom navigator.

- Entering a daughter adopted the state of the step, which could still carry the block of the volume the previous crossing left, so that volume stayed blocked one step longer than Geant4's rule allows.
- Seven of 50000 geantino rays through the ITS outer-barrel services saw up to 9 X0 too much copper because of it; they now agree with TGeo.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: sawenzel

Detectors/gconfig/src/VecGeomG4Navigator.cxx

@@ -315,6 +315,9 @@ G4VPhysicalVolume* VecGeomG4Navigator::LocateGlobalPointAndSetup(const G4ThreeVe
     // Into the daughter the step hit, then down inside it.
     mReloScratch = mCurState;
     mCurState = mNextState;
+    // mNextState is a copy of the step state and can still carry the block of the volume the previous
+    // crossing left, which was meant for the first step after that exit only.
+    mCurState.SetLastExited(mEmptyState.GetLastExitedState());
     auto const* daughter = mCurState.Top();
     mCurState.Pop();
     vecgeom::Transformation3D m;