Editing: remove workers from tiles edited to unworkable terrain
If you switch to edit mode, make radius 10 of placing Inaccessible terrain and click next to a city, its non-central workers remain where they are while the city just can't work Inaccessible. Did not check border changes by editor, probably they are correct.
Maybe applies to terrain changes in general, and not just by the editor? In fact, "Tile_Workable" effect can have any kind of requirements, so we should check legality of worker placement regularly.