Swap the compound-engineering workflow's execute seam for a compound-engineering:ce-work skill node in coding mode, so the implementation stage actually runs the CE way (R1). Add tests asserting the ce-work skill executor and coding toolMode. Part of the compound-engineering workflow integration plan (docs/plans/2026-06-13-002). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>