Make all warnings respect --warn-error Previously, resolution failures in Errors.report used Lookup_failures.report_internal which hardcoded non_fatal:true, meaning they would never cause a build failure even when --warn-error was passed. Switch to Lookup_failures.report_warning so that all resolution failures (modules, types, references, etc.) respect --warn-error. Root errors (missing dependencies) retain their own separate handling via report_root. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>