LoadingWidget

Compose the loading widget layout.

Start animation on mount.

Preserves _start_time when the widget is remounted (e.g., after being removed and re-added for repositioning) so the elapsed-time counter doesn't reset. Repositioning via move_child avoids the remount path entirely, but this guard keeps the behavior correct if any caller ever falls back to remove + mount.

Stop the animation timer when the widget leaves the DOM.

Stop animation before delegating DOM removal to Textual.

Update the status text.

Pause the animation and update status.

Resume the animation.

Stop the animation (widget will be removed by caller).