fix: use copilot engine for test-copilot-command workflow

Agent-Logs-Url: https://github.com/githubnext/gh-aw-test/sessions/ebb26e65-00e3-4963-9dd7-b35dd573b3fd

Co-authored-by: dsyme <7204669+dsyme@users.noreply.github.com>

Author: Copilot