Function on_exit_signal 

pub fn on_exit_signal(
    cmd: Commands<'_, '_>,
    pos_indicator: Single<'_, '_, Entity, With<PositionIndicator>>,
    target_segment: Res<'_, TargetSegment>,
    next_state: ResMut<'_, NextState<UiState>>,
)

Handles going out of EditorState::Signal, removing the position indicator and going back to the segment’s window.