A view-only collaborator could put the editor title into edit mode. The
rename reached the server, which refused it (FORBIDDEN), but the client
rethrew the error into runZonedGuarded, left the typed name in the field,
and stayed in edit mode, so every later focus change submitted it again
(five refused updates in one live session). The title now enters edit mode
only with the canRenameStrategy capability. For anyone, a failed rename is
handled: the previous name comes back, edit mode ends, and one message
says why ("You can't rename this strategy." for FORBIDDEN, the sync error
text otherwise), with the redacted error in the debug log.

After a share link was redeemed, the page kept its /share/<code> URL, so
every reload redeemed it again, and once the link was disabled a reload
told a user who still had access that redemption failed. When a code is
settled (redeemed, already accessible, or a failure the user was told
about), the page URL now becomes the app root, keeping the router's
fragment. A code waiting for sign-in or for the cloud to be ready is not
settled, so the pending store keeps it as before.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>