The feature file cli_version_info_diagnostics_showcase.feature was added
without corresponding Behave step definitions, causing unit_tests CI to fail
with AmbiguousStep errors. This commit adds the step definitions file and
updates the feature file step text to avoid conflicts with existing steps
in execution_environment_steps.py.
Created comprehensive showcase documentation for CLI version, info, and diagnostics commands
Documented fast-path vs regular command behavior
Included verified outputs and machine-readable JSON/YAML examples
Registered the showcase entry in docs/showcase/examples.json
Added BDD tests for the showcase documentation
Closes#7592