Function generate_dictionary_extern 

pub fn generate_dictionary_extern(
    decl: &InterfaceDecl,
    ctx: &ModuleContext,
    cgctx: Option<&CodegenContext<'_>>,
    js_namespace: Option<&str>,
    scope: ScopeId,
) -> TokenStream

Generate a simple extern “C” block for a dictionary interface. Temporary until M5 implements proper dictionary builders.