An action op that calls Phoenix.LiveView.push_event/3 on the
socket. Fires a client-side event for a JS hook to receive via
this.handleEvent("name", fn).
Payload values can be literal terms or rx(...) expressions —
rx values are evaluated against the action's effective state
(state + calculations + params) at fire time.
Example
action :inc do
set :count, rx(@count + 1)
push_event "counter_updated", %{count: rx(@count), kind: "inc"}
end