openai/gpt-chat-latest → A (5:2)

Side A introduces a substantive new hierarchical data model centered on `ItemId` and `GlobalTree`, migrates voting from flat scope strings to parent-node rankings, adds canonical Reddit URL parsing, breadcrumb navigation, node persistence (`NodeEnsured`), and a journal worker that updates the tree after durable event logging. Side B is primarily a refactor that consolidates existing `/post` endpoints into the `/ui` RPC flow, factors out shared session resolution, and rewires forms and tests; while it reduces duplication and simplifies routing, it mostly reorganizes existing behavior rather than adding comparable long-term functionality.