feat: add structured room role metadata

runners/codex-runner/src/room-role-context.ts

@@ -0,0 +1,23 @@
+export interface RoomRoleContext {
+  serviceId: string;
+  role: 'owner' | 'reviewer';
+  ownerServiceId: string;
+  reviewerServiceId: string;
+  failoverOwner: boolean;
+}
+
+export function prependRoomRoleHeader(
+  prompt: string,
+  roomRoleContext?: RoomRoleContext,
+): string {
+  if (!roomRoleContext) {
+    return prompt;
+  }
+
+  const header =
+    `[ROOM_ROLE self=${roomRoleContext.serviceId} role=${roomRoleContext.role} ` +
+    `owner=${roomRoleContext.ownerServiceId} reviewer=${roomRoleContext.reviewerServiceId} ` +
+    `failover=${roomRoleContext.failoverOwner ? 1 : 0}]`;
+
+  return `${header}\n\n${prompt}`;
+}