feat(export): export wildfire smoke only

[MateoLostanlen]

• The dataset export now returns wildfire smoke only. An alert with any lane annotated industrial or other is dropped whole, siblings included.
• Dropping just the lane is not enough: lanes of one alert share their frames, so an exported false-positive or wildfire sibling would ship images with visible, unlabeled smoke in them. The check spans every lane, unsure ones included, for the same reason.
• Always on, no new parameter. The existing smoke_types filter still works but any value other than wildfire now matches nothing.
• Not additive: alerts that used to export because their smoke sibling was industrial or other now disappear, so a pyro-dataset re-import will see fewer alerts than the run before it.