Function proxy_ack 

pub(crate) async fn proxy_ack(
    state: &AppState,
    host: &HostIpc,
    route: &str,
    body: Value,
) -> Result<(), Response>

Proxies route with body and checks the host’s {ok, ...} envelope. Shared by the write-only browser-pane tools (navigate/back/forward/ reload/focus_element/dispatch_key) — they differ only in which route/body they send, not in how they interpret an ack-only reply.