Fix the merger exit-status check in o2-sim

This fixes a problem in how the o2-sim driver judges the hit merger's exit code.

- The condition `!= 0 || != 128` is always true, so every normal merger exit was reported as an error.
- It now reads `!= 0 && != 128`.

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

Author: sawenzel

run/o2sim_parallel.cxx

@@ -763,7 +763,7 @@ int main(int argc, char* argv[])
   // Handle mergerpid status separately
   if (cpid == mergerpid) {
     if (WIFEXITED(status)) {
-      if (WEXITSTATUS(status) != 0 || WEXITSTATUS(status) != 128) {
+      if (WEXITSTATUS(status) != 0 && WEXITSTATUS(status) != 128) {
         LOG(error) << "Merger process exited with abnormal exit status " << WEXITSTATUS(status);
         errored = true;
       }