Builds and reviews custom Advanced Custom Fields field types on the Free acf_field extension API. Covers acf/include_field_types registration, initialize metadata, settings and input rendering, dynamic input names, validation, load/update/format transforms, field-aware HTML escaping, assets, REST visibility, and repeater-compatible JavaScript initialization. Use when a built-in ACF field cannot represent the editor control or stored value, when extending acf_field, or when a custom field saves correctly but formats, validates, repeats, or renders unsafely.
