Concurrent job launches can land in the same wall-clock second, causing
G4System::init's time-based seed (seed=-1) to collide and produce
byte-identical physics across separately-named shards. Falls back to
the existing time-based seed if the variable is unset, empty, or invalid.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Mirrors run_pbwo4 but alternates thin absorber and active layers,
with four selectable configs (by name or 1-based index): pb_scint,
fe_scint, w_scint_ecal (homogeneous ECAL-like preshower + W/scint
sampling section), and pb_lar. Each is sized to reach ~20-25 X0 of
absorber despite the dilution from inactive gaps. Wired into the
top-level CMakeLists, superbuild, and Dockerfile alongside run_pbwo4.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
lars