Portable training input workflow for wcgpu and sgpu (Related to WireCell/spng#39)

[physnerds]

Sub-issue for #39: portable training input workflow for wcgpu and sgpu

Issue

The training_inputs/Snakefile from git runs on wcgpu, but the sgpu machine needs different site-local resources:

• There is no /nfs file system in sgpu machine. Apptainer binding in Snakefile binding needs to address this (see the comment in Snakefile)
• the Apptainer bind list must expose GPFS paths inside the container;
• the default DUNE cosmic-generation FHiCL reads CORSIKA shower database files from CVMFS, while sgpu needs the local GPFS copy at /gpfs01/lbne/users/spng/stash/Cosmics/CERN/CORSIKA/standard.

Changes made

• Updated the top-level Snakefile to use one configurable DUNE software container path:
  • defaults to the original wcgpu container, /nfs/data/1/calcuttj/dunesw.sif;
  • auto-selects the sgpu GPFS container when /gpfs/mnt/gpfs01/lbne/users/spng/abashyal/wct-env/wire-cell-dev/container/dunesw.sif exists;
  • can be overridden explicitly with Snakemake config key dunesw_container or environment variable DUNESW_CONTAINER.
• Updated test_container, gen_cosmics, g4, and save_depos to use the shared config['dunesw_container'] value.
• Updated the Apptainer bind list in the Snakefile shebang to include both the original /nfs bind and the GPFS paths needed by sgpu.
• Added prod_cosmics_protodunehd_local.fcl, a small wrapper around prod_cosmics_protodunehd.fcl that overrides only physics.producers.cosmicgenerator.ShowerInputFiles to use the sgpu GPFS CORSIKA shower database.
• Updated gen_cosmics to take its FHiCL through params.fcl instead of hard-coding prod_cosmics_protodunehd.fcl. This preserves the original lar FHiCL lookup behavior on wcgpu, where prod_cosmics_protodunehd.fcl does not need to be a local Snakemake input.
• Added automatic FHiCL selection:
  • use prod_cosmics_protodunehd_local.fcl when the sgpu CORSIKA directory exists;
  • otherwise keep the original prod_cosmics_protodunehd.fcl behavior for wcgpu;
  • allow explicit override with Snakemake config key cosmics_fcl or environment variable COSMICS_FCL.

This keeps the git Snakefile behavior for wcgpu while folding in the sgpu fixes without maintaining a separate machine-specific Snakefile.