Migrated error()/warning() calls across 10 branches to use CLI display API
which routes to stderr. 48 files modified across ai_mail, api, backup, daemon,
flow, memory, prax, seedgo, spawn, trigger. Seedgo stderr_routing standard
created (24th standard) with full-file scanning. System average 49% → 69%.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
CLI display.py now routes error() and warning() to stderr via err_console.
Added fatal() for unrecoverable errors. Drone imports err_console from CLI
instead of creating its own. RegistryMismatchError added to drone exception
hierarchy for credential verification failures.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>