v2.6.0-beta.0

• refactor!: rename validation errors and simplify response error shape

• rename ValidationError to ResponseValidationError

• rename isValidationError to isResponseValidationError

• remove request/response from ResponseError

• add v2 to v3 upgrade guide and update docs/tests

• feat: restore deprecated validation error aliases in dist exports

• serializable errors

serializable errors

• feat(ai): add agent skill