The submodule leaves a .git *file* (not directory) pointing to
../../.git/modules/lib/geant4, which passes G4GitUtilities' guard
but causes a FATAL_ERROR when git status fails in the bare /tmp dir.
Remove .git before cmake so the guard fires and the check is skipped.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add 15 new columns to the Steps ntuple: edep, step_length, parent_id,
process name, layer_id, material, pre-step momentum direction, and
B/E field components (in T and V/m) at the pre-step point.
Replace wget Geant4 tarball download in all three Dockerfiles with
ADD of the lib/geant4 submodule source; narrow submodule init to
lib/pybind11 only so builds no longer require network access for Geant4.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>