docs(architecture): consolidate domain protocols

src/stores/private-room/private-room-context.tsx

@@ -10,6 +10,7 @@ import type {
   PrivateRoomState as MachineContext,
 } from "./private-room-machine";
 
+/** Route UI reads this projection instead of the Private Room snapshot. */
 export interface PrivateRoomContextState {
   characterId: string;
   status: string;