Add rare hidden radio easter egg transmission

src/game/game_manager.gd

@@ -458,6 +458,13 @@ func _on_radio_submitted(report: Dictionary, emergency: bool) -> void:
 		coordinator.crowd.apply_event("calm_professionalism")
 	if audio:
 		audio.play_radio_response()
+	_maybe_radio_easter_egg()
+
+## Rare hidden radio transmission: a stray voice asks "¿Dónde está la mota?"
+## over the radio. Fires on a small random chance after a successful call.
+func _maybe_radio_easter_egg() -> void:
+	if _door_rng.randf() < 0.025:
+		hud.log(Strings.lookup("radio.easter_egg"))
 
 # ----------------------------------------------------------------- access --