- main(argv) signature enables in-process CLI invocation and testing
- parser defaults for --e-step/--neutrino-mass/--intensity-cutoff/
--csv-separator/--normalize-to-one now None = 'not provided'
- JSON flow applies file values by default and CLI flags as overrides
(previously these five options were silently discarded)
- paceENSDF flow resolves None flags to literal defaults
- new tests/integration/test_cli_flows.py: JSON propagation,
degenerate-mode non-zero exit with no file (JSON + paceENSDF)
- adapted two neutrino-mass default tests to None-parsing semantics
