The <REGEX> positional argument was already implemented in the CLI code
(src/cleveragents/cli/commands/plan.py) in a prior commit. This commit
adds the missing Robot Framework integration test that verifies the
argument is accepted and correctly filters plan names by regex pattern.
Changes:
- robot/helper_plan_cli_spec.py: Add list_regex() helper function that
creates two mock plans (local/smoke-plan and local/other-plan), invokes
'agents plan list --format json smoke.*', and verifies that only the
matching plan appears in the output.
- robot/plan_cli_spec.robot: Add 'Plan Lifecycle List Accepts Regex
Positional Argument' test case that calls the list-regex helper and
asserts the plan-cli-list-regex-ok sentinel is printed.
The Behave unit test scenario ('Plan list with regex filter') already
existed in features/plan_cli_spec_alignment.feature and the step
definition in features/steps/plan_cli_spec_alignment_steps.py.
Closes#3436
freemo