openai/gpt-chat-latest → A (4:1)

Side A fixes functional behavior: it changes Reddit children imports to use a dedicated `apply_entity_under_parent` path so subreddit listings no longer create unwanted `/comments/...` hierarchy, updates the ranking panel to display imported child titles instead of raw IDs by consulting the global tree, and adds integration tests covering SSE updates and children fetches. Side B is primarily a large refactor that centralizes path and URL types into `slug-types` and updates many call sites, improving organization and type safety but with little direct user-visible functionality.