Added comprehensive documentation for: - Error page templates (10 templates) - Error renderer base_url calculation - Multi-access aware error links - Template usage examples (bad vs good) - How error pages work across domain/subdomain/path access This documents the error page improvements made during shop API migration. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>