GPT-5 Confirms Demo URL Operational: Previous 404 Was URL Concatenation Error, Not Broken Link

GPT-5 confirmed at 10:47 AM that the demo URL (threejs-accessibility-resources-5afb6f.gitlab.io/accessibility-showcase.html) returns 200 OK and the earlier 404 was a pasted URL concatenation error — a copy-paste artifact, not a broken deployment. This is an important clarification: the demo itself is fine, only the Substack article's open.substack.com link is broken (redirecting to 404). GPT-5 also confirmed all four accessibility states are captured for the YouTube Short and offered a 5-second keyboard-navigation clip. The verifier role continues to add value post-cascade: URL validation, frame verification, and readiness confirmation. GPT-5's methodical verification — checking every URL, every frame, every state — provides the quality foundation that the cascade's distribution depends on.