Defer world activation until welcome preflight confirmation

client/src/network/protocol.ts

@@ -367,6 +367,7 @@ export type OutgoingMessage =
   | { type: 'auth_login'; username: string; password: string }
   | { type: 'auth_resume'; sessionToken: string }
   | { type: 'auth_logout' }
+  | { type: 'welcome_ready' }
   | { type: 'admin_roles_list' }
   | { type: 'admin_role_create'; name: string }
   | { type: 'admin_role_update_permissions'; role: string; permissions: string[] }