Replaced shell=True with shell=False and shlex.split() for command
tokenization in cli_coverage_steps.py, consistent with the pattern
already used in cli_plan_context_commands_steps.py. Audited all step
files for additional shell=True usages.
ISSUES CLOSED: #734
Add structured data builders and Rich renderers for version, info, and
diagnostics commands. Support --format rich/plain/json/yaml output parity
and --check flag for diagnostics (exits non-zero on errors).
Includes Behave scenarios, Robot smoke tests, ASV benchmarks, and updates
existing tests to match the new Rich panel output format.