The TDD regression files for bug #968 were incorrectly deleted instead of
updated to assert the spec-compliant fixed behaviour from issue #6325.
Per CONTRIBUTING.md the regression guard must be kept and updated — not
removed — once the bug is fixed.
Restore and update all three files to assert the new expected behaviour:
- plan explain rejects a non-decision-id argument with rc=1
- error output contains "not found"
- decision data fields are absent from output
Also pair the orphaned robot/helper_tdd_plan_explain_plan_id.py with a
restored robot test file and update it to verify rc=1 rejection behaviour.
ISSUES CLOSED: #6325
- Shorten error message in explain_decision_cmd to fit 88-char limit (E501)
- Add `from None` to raise typer.Exit(1) inside except block (B904)
- Fix step definition mock to raise DecisionNotFoundError instead of
returning None, so the exception handler fires and output contains
"not found" as the scenario asserts
ISSUES CLOSED: #6325
HAL9000