Cascades .buttonStyle(.plain) down from each LCENavigationView
instance instead of waiting on the LCEssentials package fix
(committed separately, unpublished: LC_Essentials commit 8b0f650) to
be released and this repo's Package.resolved bumped. Overrides
iOS 26's automatic Liquid Glass chrome on LCENavigationView's
internal nav buttons - including the invisible backfilled mirror
button on whichever side has no real action - without affecting any
button that already sets its own explicit style closer to itself.
29c80d06af