validation

• Core Validators

  Trait-based validation primitives covering presence, type, string, format, numeric, datetime, choice, collection, comparison, conditional, composite, and domain rules — composed into payload `validate()` methods that the framework runs automatically before handlers.

• UI Field Validation

  The server-side rules DSL for platform-ui fields, including cross-field rules such as sameAsField.

• Payload Validation

  Where validation sits in the pipeline, how payload rules and helpers are written, hydration, the failure response, and session and cookie payloads.