151 pointfree chain threads whole input

// Pins the point-free `|>` chain with its fifth check: a bare stage stands for
// "the thread supplies this stage's WHOLE input". Each stage carries the real
// two-branch shape (`| ctx` threaded, `| failed` harvested) so `| ctx` is a
// named branch the `|>` can pun into the next `ctx` input — no `(ctx: cN)`
// binder, no per-stage `failed` re-raise. The single trailing `| failed` arm
// chokes the whole chain; the terminal `ctx` matches `run`'s declared `| ctx`
// so it emits with no identity arm.  stage-a(2) => 3, stage-b(3) => 6.
~import std/io

~pub tor stage-a { ctx: i64 }
| ctx i64
| failed string
~proc stage-a|zig { return .{ .ctx = ctx + 1 }; }

~pub tor stage-b { ctx: i64 }
| ctx i64
| failed string
~proc stage-b|zig { return .{ .ctx = ctx * 2 }; }

~pub tor run { ctx: i64 }
| ctx i64
| failed string
~run = stage-a
  |> stage-b
| failed f => failed f

~run(ctx: 2)
| ctx c |> std/io:print.ln("{{ c:d }}")
| failed f |> std/io:print.ln("err")