Follow-up from #239 optional-field audit.

The audit must classify clients.update optional WSDL rows without generic candidates. Current CLI exposes selected client update fields, while WSDL contains nested Notification, Settings, TinInfo, and ErirAttributes structures.

Scope includes Notification.Email, EmailSubscriptions, Settings.Option/Value, ErirAttributes Organization/Contract/Contragent, and other rows reported by tests/WSDL_OPTIONAL_FIELD_AUDIT.md.