openai/gpt-chat-latest → B (9:1)

Side B introduces substantial new functionality and architecture: explicit user-triggered Reddit entity fetching, persistent `EntityImported` events with replay support, storage of raw API payloads plus derived views, configurable API endpoints, dotenv loading, and accompanying UI, tests, and fixtures. Side A is a focused correctness fix that makes `thread_post_index` consistently 0-based by replacing a silent fallback with `expect`, updating documentation, always rendering the link, and adding integration tests, but its scope and lasting impact are much smaller.