The preview browser is a Chromium guest the desktop app hosts, so its defaults
mean nothing in a web client. They are also client-local, which is why these
are disabled rather than hidden: editing them from a browser tab would write
preferences belonging to a different client, reading as though the desktop app
had been configured when it hadn't.

Follows the pattern Keybindings already uses for a desktop-only concern — an
inline notice above the affected controls. Reset affordances are withheld too,
since there is nothing to reset from here.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>