Function build_handler_set 

pub fn build_handler_set(
    catalog: &Catalog,
    queries: &[AnalyzedQuery],
    info: &OpenApiInfo,
    opts: &BuildOptions,
    languages: &[LanguageBackend<'_>],
) -> Result<HandlerSet, RouteBuildError>

Walk a slice of analyzed queries and build the full handler set: routes, OpenAPI spec, and a per-language sidecar. Queries without an @http directive are skipped silently. The sidecar is populated by passing per- language lang_type_for resolvers in languages.

languages maps language name → (scythe_module, scythe_fn_for, is_async, lang_type_for) tuples. The closures are evaluated once per query, giving callers full control over per-language naming and type resolution without pulling scythe’s backend trait into this crate’s surface.