The NIBArchive value decoder read type tag 4 as true and 5 as false, the
reverse of what ibtool writes and AppKit's decoder returns, so every
compiled-nib boolean in decode-interface-builder output was inverted. The
test fixture encoder shared the reversed mapping, hiding it in round trips.
Name the value-type tags once and use them in both the read and skip
paths, fix the fixture encoder, pin raw tags in a unit test, and make
verify:interface-builder compare both polarities with ibtool --export.
Fixes#5541
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
