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, 1 deletions

diff --git a/README.md b/README.md
index b5d3362..f6e782d 100644
--- a/README.md
+++ b/README.md
@@ -669,11 +669,12 @@ With the `general_renderer` feature, users can add `--json` or `--yaml` flags to
 
 use mingling::{prelude::*, setup::GeneralRendererSetup};
 use mingling::Groupped;
+use mingling::StructuralData;
 use serde::Serialize;
 
 dispatcher!("render", CMDRender => EntryRender);
 
-#[derive(Default, Serialize, Groupped)]
+#[derive(Default, StructuralData, Serialize, Groupped)]
 struct ResultInfo {
     name: String,
     age: i32,