Backfill step definitions should populate or remove unused parameter_ids tracker

[kbighorse]

Context

Identified during review of #558 (558-radionuclides-backfill branch).

Problem

_ensure_backfill_tracking in chemistry-backfill.py initializes a parameter_ids list in _backfill_created, but nothing ever appends to it. This creates confusion about whether Parameter cleanup is handled.

Fix

Either populate parameter_ids when _get_or_create_parameter creates new Parameters and clean them up in after_scenario, or remove the unused key to avoid misleading future developers.

Files

• tests/features/steps/chemistry-backfill.py (line ~52, _ensure_backfill_tracking)

[github-actions]

Linked Jira ticket created: BDMS-619