Function set_webcam_bubble_visibility_js 

pub async fn set_webcam_bubble_visibility_js(
    visible: bool,
) -> Result<JsValue, JsValue>

__screenSetBubbleVisibility(visible) in index.html — returns Promise<void>. ISS-05 fix; explicit setter so the recorder’s camera_enabled signal can drive the bubble’s visibility without the toggle-drift the always-flip path had.