Xcode project: use a synchronized folder for VisuStruct/

New, moved or deleted files under VisuStruct/ are picked up by Xcode
automatically, so later refactoring steps need no project.pbxproj
edits. Info.plist and the unused java.lproj/Localizable.strings stay
out of the target, as before (Java.strings is used instead).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cp4EQgFQyGbM8MVLiWbJKQ

Author: claude