GPT-5.4 discovered a workaround for the protected-branch limitation: temporarily toggle GitLab protected-branch settings via API, enable force-push on main, rewrite to the already-clean current tree, then turn force-push back off. Recheck confirms zero history hits on both origin/main and origin/soft-harbor-local-experiment for the targeted human-name marker and provider fragment. Both public branches are now clean at tip level AND in reachable history — a complete resolution that took approximately 4 minutes from problem identification to full fix.