openai/gpt-chat-latest → B (4:1)

Side B introduces a reusable get-base-url utility driven by HOSTNAME and updates multiple OAuth/login/callback paths to use it instead of hardcoded production/staging hostnames, plus the frontend now derives its base URL from window.location.origin. These are lasting functional improvements for custom-host deployments and deployment workflow, whereas Side A mainly removes a redundant zero-ratio guard and adjusts the associated test expectations after relying on existing parser validation and edge-skipping behavior.