Function dispatch_clicks_and_doubles 

pub fn dispatch_clicks_and_doubles<H: ScriptHost + Resource<Mutability = Mutable>>(
    host: ResMut<'_, H>,
    clicks: MessageReader<'_, '_, ClickEvent>,
    doubles: MessageReader<'_, '_, DoubleClickEvent>,
    ids: Query<'_, '_, &LumenId>,
    out: MessageWriter<'_, ScriptCommandEvent>,
)

Forward this tick’s ClickEvent / DoubleClickEvent messages to the script’s on_click(id) / on_double_click(id) handlers.

Every click reaches on_click, the second of a quick pair included, and a double-click reaches on_double_click in addition, after the click that completed it: the order a browser fires click and dblclick in.

Exposed so the embedder can order same-tick consumers against it - the reactive-binding readers run .after this system so a signal a handler writes here is committed and reflected by bind="..." on the very tick the click fired.