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, 1 insertions, 1 deletions

diff --git a/docs/pages/concepts/4-program-collect.md b/docs/pages/concepts/4-program-collect.md
index c5203c3..bc1fbc9 100644
--- a/docs/pages/concepts/4-program-collect.md
+++ b/docs/pages/concepts/4-program-collect.md
@@ -9,7 +9,7 @@ Every Mingling program ends with a `gen_program!()` call. Behind the scenes, it
 
 ### 1. Generate an enum
 
-Scans the current module for all types marked with `pack!`, `#[chain]`, `#[renderer]` and similar macros, then generates an enum variant for each type.
+Scans the current module for all types marked with `#[derive(Grouped)]`, `#[chain]`, `#[renderer]` and similar macros, then generates an enum variant for each type.
 
 This enum is the type of `G` in `AnyOutput<G>` — the scheduler uses enum variants to distinguish different data flowing through the pipeline.