Leave the editor itself on lost access; recheck access before a page copy

Back to library first takes down anything open over the editor, so the
editor route is what leaving pops. Copy to next/previous page checks
edit access again after reading the target page, as a reader who was
just demoted can still read it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
223a117940Dara Adedeji committed on 10/13/2026, 4:08:13 AMparent0cfefbc

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