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, 3 insertions, 2 deletions

diff --git a/mingling/src/docs/lib.md b/mingling/src/docs/lib.md
index 91858d0..3b1f328 100644
--- a/mingling/src/docs/lib.md
+++ b/mingling/src/docs/lib.md
@@ -29,12 +29,13 @@ fn main() {
     program.exec_and_exit();
 }
 
-pack!(ResultName = String);
+#[derive(Grouped, Wrap)]
+pub struct ResultName(String);
 
 #[chain]
 fn handle_greet(args: EntryGreet) -> Next {
     let name: ResultName = args
-        .inner
+        .0
         .first()
         .cloned()
         .unwrap_or_else(|| "World".to_string())