feat(core): decouple structured output from Groupped trait

Introduce `StructuralData` sealed trait and `pack_structural!` /
`group_structural!` / `derive(StructuralData)` macros to control
structured rendering separately from grouping. `Groupped` no longer
requires `Serialize`.

1 files changed, 2 insertions, 10 deletions

diff --git a/mingling_macros/src/pack.rs b/mingling_macros/src/pack.rs
index ffb07f2..5a6ccb0 100644
--- a/mingling_macros/src/pack.rs
+++ b/mingling_macros/src/pack.rs
@@ -34,7 +34,8 @@ pub fn pack(input: TokenStream) -> TokenStream {
     let attrs = pack_input.attrs;
 
     // Generate the struct definition
-    #[cfg(not(feature = "general_renderer"))]
+    // Note: No longer derives Serialize under general_renderer.
+    // Use pack_structual! for structured output support.
     let struct_def = quote! {
         #(#attrs)*
         pub struct #type_name {
@@ -42,15 +43,6 @@ pub fn pack(input: TokenStream) -> TokenStream {
         }
     };
 
-    #[cfg(feature = "general_renderer")]
-    let struct_def = quote! {
-        #(#attrs)*
-        #[derive(serde::Serialize)]
-        pub struct #type_name {
-            pub(crate) inner: #inner_type,
-        }
-    };
-
     // Generate the new() method
     let new_impl = quote! {
         impl #type_name {