`Roles.new_role` returned the result of `error`, which made it nullable,
and `set_permission_group` returned nil for an unknown group, which
broke the config chain with an index error rather than saying so.
Positions and bounding boxes read back from the game always use the
named members, so they are narrowed once where they enter a function.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>