openai/gpt-chat-latest → A (5:1)

Side A changes the authentication flow to return HTML fragments instead of redirects, adds reusable auth fragments, updates the shared Poem JS form handler to morph returned HTML into the form, and integrates the pages with the common layout, providing a lasting UX and architectural improvement. Side B is a small cleanup that removes a redundant zero-ratio guard in the reducer and updates tests to match existing behavior, which is useful but much narrower in impact.