brokerd makes a socket's directory 0700. With a socket directly in / it would
chmod /, and through a symbolic link it would change the link's target. Both
are now refused at start with #brokerd-start-failed. Without the fix the link
case started and served, with the shared directory made private.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>