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-command-macro/src/main.rs b/examples/example-command-macro/src/main.rs
index e525098..6740518 100644
--- a/examples/example-command-macro/src/main.rs
+++ b/examples/example-command-macro/src/main.rs
@@ -22,27 +22,30 @@ fn main() {
     ThisProgram::new().exec_and_exit();
 }
 
-pack!(ResultGreeting = String);
-pack!(ResultGoodbye = ());
+#[derive(Grouped, Wrap)]
+pub struct ResultGreeting(String);
+
+#[derive(Grouped)]
+pub struct ResultGoodbye;
 
 // --------- IMPORTANT ---------
 // Auto-generates dispatcher!("hello.world", EntryHelloWorld);
 #[command]
 fn hello_world() -> ResultGreeting {
-    ResultGreeting::new("World".to_string())
+    ResultGreeting("World".to_string())
 }
 
 // Auto-generates dispatcher!("hello-world", EntryGreetSomeone);
 #[command(node = "greet-someone")]
 fn greet_someone(args: Vec<String>) -> ResultGreeting {
     let name = args.pick_or(&arg![String], || "World".to_string()).unwrap();
-    ResultGreeting::new(name)
+    ResultGreeting(name)
 }
 
 // Auto-generates dispatcher!("goodbye", EntryGoodBye);
 #[command(entry = EntryGoodBye)]
 fn goodbye() -> ResultGoodbye {
-    ResultGoodbye::default()
+    ResultGoodbye
 }
 // --------- IMPORTANT ---------