~anthropic/claude-sonnet-latest → B (6:4)

Side B ships concrete, testable value: it fixes a real bug where private-room item/thread URLs in RPC responses were always emitted as public-scope paths (ambiguous/broken for room-scoped API consumers), adds new unit tests for that fix, and implements a proper server-rendered theme-cookie mechanism (replacing pure client-side localStorage switching) wired through all page handlers. Side A is a large but largely mechanical rename/refactor of `CanonicalItemUrl` into an `ItemId` enum whose variants all just wrap `String`s (little added type safety), is behaviorally equivalent to before, and its main artifact of substance—deleting a planning doc—doesn't itself add project value; per the stated preference for real bugfixes over renames/churn, B edges out.