The navigator's buttons were painted only and its number was always 1,
and Fit Artboard in Window and Actual Size always used the first
artboard. The per-document View now keeps the navigator's artboard; the
new view.goToArtboard UI command (an index, or first / previous / next /
last) sets it and fits it in the window, and the four buttons call it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>