Summary

• Extract release argument parsing and usage rendering into base_release.release_parser.
• Keep base_release.engine focused on dispatching release commands and building release context.
• Add a structure test that keeps parser helpers split from the engine.

Closes #1470

Validation

• PYTHONPATH=lib/python:cli/python $HOME/.base.d/base/.venv/bin/python -m pytest cli/python/base_release/tests/test_engine_structure.py::test_release_parser_helpers_are_split_from_engine -q
• PYTHONPATH=lib/python:cli/python $HOME/.base.d/base/.venv/bin/python -m pytest cli/python/base_release/tests/test_engine_structure.py cli/python/base_release/tests/test_engine.py -q
• PYTHONPATH=lib/python:cli/python $HOME/.base.d/base/.venv/bin/python -m pytest cli/python/base_release/tests -q
• PYTHONPATH=lib/python:cli/python $HOME/.base.d/base/.venv/bin/python -m pylint cli/python/base_release/engine.py cli/python/base_release/release_parser.py cli/python/base_release/tests/test_engine_structure.py
• PYTHONPATH=lib/python:cli/python $HOME/.base.d/base/.venv/bin/python -m compileall -q cli/python/base_release/engine.py cli/python/base_release/release_parser.py cli/python/base_release/tests/test_engine_structure.py
• git diff --check
• env BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash BASE_CACHE_DIR=/private/tmp/base-1470-release-smoke bin/basectl release plan --version 1.6.1 --manifest base_manifest.yaml