Get the streaming suggestion snapshot (`{inFlight, last}`) for a chat room, proxied from copilot-service. Powers the initial load of the composer suggestion card (mid-stream join + post-refresh render); live updates are pushed separately via the `copilotStreamEvent` SignalR event. FAIL-OPEN: copilot-service being unconfigured, slow or down yields an empty snapshot (200 with both fields null), never an error — the dashboard degrades to "no suggestion yet".

The streaming-era snapshot for a chat room, served to the dashboard by GET /v1/chat/rooms/{roomId}/suggestions. Mirrors the copilot-service internal response (GET /internal/rooms/{roomId}/suggestions). Infoset.Service.InternalApi.RoomStreamSnapshotDto.InFlight is the Redis stream accumulator (non-null while a suggestion is streaming — the dashboard bootstraps the partial text from it and then applies live copilotStreamEvent pushes with a higher seq); Infoset.Service.InternalApi.RoomStreamSnapshotDto.Last is the most recent persisted suggestion. Both null means no suggestion yet (or the proxy failed open).