Function emit_event_to_top_level_windows 

pub fn emit_event_to_top_level_windows(
    state: &AppState,
    event: &str,
    payload: &Value,
)

Emit an event to every TOP-LEVEL window — i.e. the host frontend renderers, excluding pane child browsers. Use this instead of emit_event_all_windows when the payload carries metadata that shouldn’t be visible to untrusted remote content loaded inside a browser pane. The host frontend’s listenEvent lives in the top-level renderer; pane main frames load arbitrary URLs.