Two bugs from the first on-device run.
The card sized itself from a layout it also centered, which resolved to zero, so
mask claimed a zero-size input region: the chip painted but no tap landed. Card
now sizes from the layout's implicit size and the background is a plain Item
child, not layout-managed.
wl-paste --watch replays the existing selection on start, so every watcher
restart (every unlock) resurrected a stale selection that could never be cleared
because the primary buffer never changed again. The first emission after a start
now only sets the baseline, and a dismissed selection is remembered so a re-read
cannot revive it.
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