Add CORSIKA CLI path and interaction arguments

[GernotMaier]

Summary

Add explicit CORSIKA CLI options for runtime paths and interaction models, and centralize all simulation software defaults into a single module.

What changed

New configuration/defaults.py module — single source of truth for configurable fallback values:

• CORSIKA_PATH, CORSIKA_INTERACTION_TABLE_PATH
• CORSIKA_HE_INTERACTION (epos), CORSIKA_LE_INTERACTION (urqmd)
• SIMULATION_SOFTWARE_CHOICES, SIMULATION_SOFTWARE_DEFAULT
• CURVED_ATMOSPHERE_MIN_ZENITH_ANGLE_DEG

CLI (commandline_parser.py):

• Add --corsika_path and --corsika_interaction_table_path to the paths argument group (no parser-level defaults; resolved via settings.py so env vars work)
• Add a new corsika configuration argument group with --corsika_he_interaction and --corsika_le_interaction
• Replace literal simulation-software choices/default and curved-atmosphere angle with defaults constants

Settings (settings.py):

• Fix _get_config_value to skip None arg values, so environment variables are not shadowed by unset CLI args
• Use defaults constants for CORSIKA path and interaction fallbacks
• Guard CORSIKA executable resolution with Path.is_dir() to avoid errors on non-existent default paths
• Fix docstring: priority order is CLI arg > env var > built-in default

simulator.py: replace literal simulation-software default and choices list with defaults constants

Integration test configs (simulate_prod_*.yml): add corsika_he_interaction and corsika_le_interaction to all 8 configs

CI (CI-integrationtests.yml): remove SIMTOOLS_CORSIKA_HE_INTERACTION / SIMTOOLS_CORSIKA_LE_INTERACTION echo lines — these variables were never set in the template, so they wrote empty strings that silently shadowed the built-in defaults

Docs: add defaults module to docs/source/api-reference/configuration_module.md

Validation

pytest tests/unit_tests/configuration/test_commandline_parser.py tests/unit_tests/test_settings.py tests/unit_tests/corsika/ tests/unit_tests/test_simulator.py

203 tests pass.

[Copilot]

Pull request overview

Adds explicit CLI/configuration support for CORSIKA runtime paths and interaction models, and centralizes simulation-software defaults in a single module.

Changes:

• Introduce simtools.configuration.defaults as the centralized source for simulation defaults (CORSIKA paths/models, simulation-software choices, curved-atmosphere threshold).
• Update CLI parsing and settings resolution to use centralized defaults and improve precedence handling for unset CLI args.
• Update simulator wiring plus integration-test configs/docs/CI templates to reflect the new configuration surface.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/simtools/configuration/defaults.py	Adds centralized default constants for CORSIKA and simulation configuration.
src/simtools/configuration/commandline_parser.py	Adds CORSIKA path + interaction CLI args and replaces inline literals with defaults.
src/simtools/settings.py	Uses defaults, fixes config precedence for None args, and guards CORSIKA path resolution.
src/simtools/simulator.py	Switches simulation-software defaults/choices and curved-atmosphere threshold to defaults.
tests/unit_tests/test_settings.py	Adds unit coverage for default CORSIKA paths and default interaction-model-based executable naming.
tests/integration_tests/config/simulate_prod_proton_20_deg_north_check_output.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_htcondor_generator_gamma_20_deg_north.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_gamma_62_deg_south_check_output.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_gamma_40_deg_south_sim_telarray_only.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_gamma_40_deg_south_corsika_only.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_gamma_40_deg_south_check_output.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_gamma_40_deg_north_check_output.yml	Adds explicit corsika_*_interaction fields to integration config.
tests/integration_tests/config/simulate_prod_gamma_20_deg_south_multiple_model_versions.yml	Adds explicit corsika_*_interaction fields to integration config.
docs/source/api-reference/configuration_module.md	Adds API-reference entry for the new defaults module.
docs/changes/2137.feature.md	Adds changelog fragment for the new CLI options.
.github/workflows/CI-integrationtests.yml	Stops echoing unset CORSIKA interaction env vars into .env during CI.
.github/copilot-instructions.md	Documents requirement to add new modules to API reference.
.env_template	Removes interaction-model env vars from template (defaults now provided in code).

[ctao-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube