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

Side A is a solid, focused fix that centralizes hostname/base-URL logic into one util function, removing duplicated hardcoded strings across multiple files—clear, low-risk improvement. Side B is a larger, more substantive change that removes an entire unused ThreadVisibility concept from events, reducer, timeline, RPC, CLI, and tests, simplifies rooms from a HashMap to a HashSet, adds a new CLI `room create` command with documentation, and updates integration tests—representing more real design simplification and feature completion across the stack, despite being messier and touching more files/tests.