Derive Macro ConfigShape 

#[derive(ConfigShape)]
{
    // Attributes available to this derive:
    #[shape]
}

Derive ConfigShape for a struct with named fields, or for an enum whose variants are all unit.

A struct becomes a record; each field’s schema is its type’s, its doc is its /// comment, and its required comes from the TYPE — an Option<T> field is optional and everything else is required. That is the reason there is no #[shape(optional)] attribute: the type already says it, and a second place to say it is a second place to disagree.

An all-unit enum becomes an enum-of over its variants kebab-cased, which is the spelling :set completion and :customize show. A data-carrying variant is rejected rather than flattened — a tagged union has no config-schema arm, and inventing one silently would produce a shape the host validates against wrongly.

Field names cross kebab-cased, matching the option-name convention (todo-keywords, not todo_keywords) so a TOML key reads the way every other key in the file does.