openai/gpt-chat-latest → B (4:1)

Side B fixes concrete functional issues in Reddit imports by replacing the simple `link_child` path with `apply_entity_under_parent`, which imports entity data while avoiding incorrect `ensure_path` nesting of `/comments/...` segments. It also improves the ranking UI by showing imported child titles instead of raw IDs and adds integration tests covering children fetches, SSE morphs, and the corrected import behavior; Side A is a substantial architectural addition for a unified `/ui` endpoint, but much of it is infrastructure and refactoring rather than an immediately verified bug fix.