Count the charge of the buffered TPC hit in the electron counter

This fixes the electron count that the TPC detector prints at the end of a run.

- The charge of the buffered hit was read after it had been reset to -1.
- It is now added before the reset.

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

Author: sawenzel

Detectors/TPC/simulation/src/Detector.cxx

@@ -278,10 +278,10 @@ Bool_t Detector::ProcessHits(FairVolume* vol)
     // add last buffered hit, which was not yet added to the current group
     if (mHitLast.GetEnergyLoss() >= 0) {
       mCurrentGroup->addHit(mHitLast.GetX(), mHitLast.GetY(), mHitLast.GetZ(), mHitLast.GetTime(), mHitLast.GetEnergyLoss());
-      mHitLast.mELoss = -1;
       mGroupCounter++;
       mHitCounter++;
       mElectronCounter += mHitLast.GetEnergyLoss();
+      mHitLast.mELoss = -1;
     }
   }
   // finish group