A barrel's 'module NAME' makes its directory a module; a declaration other modules
use says 'export'. Private use from another module is an error naming the module
and where to mark it; 'friend module' sees everything (a test harness); a file in
no module is public and a package keeps its own module. LUDIC_VIS_REPORT=1 lists
every violation instead of stopping, so a codebase can be given its exports first.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
