Discard a people import

The "Discard" of the "import in progress" card. needs_name and failed: deleted for good (the R2 crops and originals no row cites, then the state). done: only hides the card, the saved person is untouched. processing: 409, a running import cannot be stopped from here (a dead one is first marked interrupted and can then be discarded). Another user's import answers 404 like a missing one.