The copy now walks the source tree item by item, checking cancellation
between items, and the in-progress banner row carries its promised
Cancel — a cancelled duplicate removes the partial sibling and never
happened (DESIGN/03 > File menu). A sandbox permission refusal of the
silent Finder-style sibling falls back to an NSSavePanel pre-filled with
the parent folder and the copy name — the panel's grant is the sandbox's
own answer; cancelling the panel cancels quietly, and non-permission
failures keep the ordinary one-shot banner. Refusal classification is
deliberately narrow (NSFileWriteNoPermissionError itself, no underlying-
chain walk) so an unreadable source never masquerades as a destination
refusal. Directories are created writable first with mode and timestamps
restored after the subtree lands, so a read-only source folder can't
strand its own copy. BoardDuplicatorTests grows from 9 to 18 tests.
Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY
rzen
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