feat(config): route SEvt output directory through app config (#322)

This PR makes `gphox::Config` the authoritative source for runtime
configuration parameters that are applied to supported binaries
execution. The main focus is refactoring event runtime controls,
especially `event.mode` and `event.output_dir`, so they are read from
the app config JSON and then synchronized into `SEventConfig` from one
place.

- Added `--config` support to the affected binaries so runtime behavior
can be selected via config file.
- Updated tests/scripts to use the config-controlled output location
instead of relying on fake `USER`/`GEOM` environment setup.
- Eliminated the need to set `USER` and `GEOM` environment variables for
the supported binaries/tests that now route output through `Config`.

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: plexoos

config/dev.json

@@ -25,6 +25,7 @@
 
   "event": {
     "mode": "DebugLite",
-    "maxslot": 1000000
+    "maxslot": 1000000,
+    "output_dir": "./"
   }
 }

src/GPUCerenkov.cpp

@@ -13,6 +13,7 @@
 #include "sysrap/OPTICKS_LOG.hh"
 
 #include "GPUCerenkov.h"
+#include "config.h"
 
 #include "G4RunManager.hh"
 #include "G4RunManagerFactory.hh"
@@ -56,7 +57,7 @@ int main(int argc, char **argv)
 
     argparse::ArgumentParser program("GPUCerenkov", "0.0.0");
 
-    string gdml_file, macro_name;
+    string gdml_file, config_name, macro_name;
     bool interactive;
 
     program.add_argument("-g", "--gdml")
@@ -65,6 +66,12 @@ int main(int argc, char **argv)
         .nargs(1)
         .store_into(gdml_file);
 
+    program.add_argument("-c", "--config")
+        .help("the name of a config file")
+        .default_value(string("dev"))
+        .nargs(1)
+        .store_into(config_name);
+
     program.add_argument("-m", "--macro")
         .help("path to G4 macro")
         .default_value(string("run.mac"))
@@ -87,6 +94,8 @@ int main(int argc, char **argv)
         exit(EXIT_FAILURE);
     }
 
+    gphox::Config{config_name};
+
     // Configure Geant4
     // The physics list must be instantiated before other user actions
     G4VModularPhysicsList *physics = new FTFP_BERT;

src/GPUPhotonFileSource.cpp

@@ -14,6 +14,7 @@
 #include "sysrap/OPTICKS_LOG.hh"
 
 #include "GPUPhotonFileSource.h"
+#include "config.h"
 
 using namespace std;
 
@@ -23,7 +24,7 @@ int main(int argc, char **argv)
 
     argparse::ArgumentParser program("GPUPhotonFileSource", "0.0.0");
 
-    string gdml_file, macro_name, photon_file;
+    string gdml_file, config_name, macro_name, photon_file;
     bool interactive;
 
     program.add_argument("-g", "--gdml")
@@ -32,6 +33,12 @@ int main(int argc, char **argv)
         .nargs(1)
         .store_into(gdml_file);
 
+    program.add_argument("-c", "--config")
+        .help("the name of a config file")
+        .default_value(string("dev"))
+        .nargs(1)
+        .store_into(config_name);
+
     program.add_argument("-p", "--photons")
         .help("path to input photon text file (one photon per line: pos_x pos_y pos_z time mom_x mom_y mom_z pol_x "
               "pol_y pol_z wavelength)")
@@ -75,6 +82,8 @@ int main(int argc, char **argv)
     CLHEP::HepRandom::setTheSeed(seed);
     G4cout << "Random seed set to: " << seed << G4endl;
 
+    gphox::Config{config_name};
+
     // Configure Geant4
     // The physics list must be instantiated before other user actions
     G4VModularPhysicsList *physics = new FTFP_BERT;

src/GPURaytrace.cpp

@@ -13,6 +13,7 @@
 #include "sysrap/OPTICKS_LOG.hh"
 
 #include "GPURaytrace.h"
+#include "config.h"
 
 #include "G4RunManager.hh"
 #include "G4RunManagerFactory.hh"
@@ -53,7 +54,7 @@ int main(int argc, char **argv)
 
     argparse::ArgumentParser program("GPURaytrace", "0.0.0");
 
-    string gdml_file, macro_name;
+    string gdml_file, config_name, macro_name;
     bool interactive;
 
     program.add_argument("-g", "--gdml")
@@ -62,6 +63,12 @@ int main(int argc, char **argv)
         .nargs(1)
         .store_into(gdml_file);
 
+    program.add_argument("-c", "--config")
+        .help("the name of a config file")
+        .default_value(string("dev"))
+        .nargs(1)
+        .store_into(config_name);
+
     program.add_argument("-m", "--macro")
         .help("path to G4 macro")
         .default_value(string("run.mac"))
@@ -98,6 +105,8 @@ int main(int argc, char **argv)
     CLHEP::HepRandom::setTheSeed(seed);
     G4cout << "Random seed set to: " << seed << G4endl;
 
+    gphox::Config{config_name};
+
     // Configure Geant4
     // The physics list must be instantiated before other user actions
     G4VModularPhysicsList *physics = new FTFP_BERT;