files: don't open the Move picker inside the item being moved #278

Parent: #14 · Found by the local review of #277.

With "Remember target folder" on, the Move picker can open at a remembered folder that sits deeper inside the item being moved. #277 catches the folder itself and a direct child, but a deeper descendant needs the folder's ancestry, which FilesRepository doesn't expose (no breadcrumbs).

First check whether put.io already refuses a move into the item's own descendant (a --dry-run-free check needs a disposable fixture on devs-auto, created and removed by the test). If it does, Android only needs to show that refusal clearly (#274 covers the reason text); if not, read breadcrumbs through the SDK and open at root when any ancestor is the moved item.

If put.io allows the move, the fallback needs an SDK change: FileBreadcrumb exists but no response exposes it.