Dropbox is case insensitive and the path_display it returns in
change notifications may not match the case of the configured root.
Before this change the root was trimmed with a case sensitive prefix
match, so when the cases differed the full path was passed to the
ChangeNotify callback and the notification was ignored.
This trims the root case insensitively while preserving the display
case of the remaining path.
Direct lookups of exported Dropbox Paper files retained the
caller-visible extension before export metadata processing appended it
again. Track when metadata was resolved through an export path so the
object keeps the requested remote name while listing behavior remains
unchanged.