pub(crate) fn parse_field_attrs(field: &Field) -> Result<FieldAttrs>Expand description
Parse field-level #[dataframe(...)] attributes from a syn::Field.
Recognizes: skip, rename, as_list, as_factor, expand (alias unnest), and width.
Validates mutual exclusivity of conflicting options (as_list vs expand/width,
as_factor vs as_list/expand/width).
Returns Err for unknown keys, invalid width values, or conflicting options.