refactor!: replace pack! macros with derive-based pipeline types

Remove the `pack!`, `pack_err!`, `pack_structural!`, and
`pack_err_structural!` macros, replacing all pipeline type definitions
with `#[derive(Grouped)]` and `#[derive(Grouped, Wrap)]` attributes.
This changes the generated struct shape from named-field structs with an
`inner` field to tuple structs accessed via `.0`, and removes the
auto-generated `name` and `info` fields from error types.

1 files changed, 8 insertions, 5 deletions

diff --git a/examples/example-exitcode/src/main.rs b/examples/example-exitcode/src/main.rs
index d3e035e..c7f731d 100644
--- a/examples/example-exitcode/src/main.rs
+++ b/examples/example-exitcode/src/main.rs
@@ -36,18 +36,21 @@ fn main() {
 
 dispatcher!("hello", EntryHello);
 
-pack!(ErrorNoNameProvided = ());
-pack!(ResultName = String);
+#[derive(Grouped)]
+pub struct ErrorNoNameProvided;
+
+#[derive(Grouped, Wrap)]
+pub struct ResultName(String);
 
 #[chain]
 fn handle_hello(args: EntryHello) -> Next {
-    let Some(name) = args.inner.first().cloned() else {
+    let Some(name) = args.0.first().cloned() else {
         // If no name is provided, pass ErrorNoNameProvided
-        return ErrorNoNameProvided::default().to_render();
+        return ErrorNoNameProvided.to_render();
     };
 
     // If the name is valid, pass ResultName
-    ResultName::new(name).to_render()
+    ResultName(name).to_render()
 }
 
 /// Renders a successful greeting with the given name.