192 unbound effect payload threads by type

// PINS: an UNBOUND effect payload threads into the next stage by TYPE.
//
// `! emit` carries a string and writes no binder. `render-at` has `x` written,
// so `text` is its only unfilled parameter and the arriving payload is a
// string — exactly one candidate, so it lands there. The effect is named `emit`
// and the parameter is named `text`: nothing puns.
//
// 210_157 is the BOUND spelling of this same program, where the binder's name
// and the parameter's name happen to coincide and the payload fills by pun.
// That test states how a NAMED payload moves; this one states how an unnamed
// one does. Selection by type needs no such coincidence, which is what makes it
// the rule that generalises — `emit`/`text` share nothing here.
//
// Sibling of 210_191, the obligation-branch twin (`| lo`). One check refuses
// both positions today, so they move together.
const std = @import("std");
~tor render-at { x: i64, text: string }
~proc render-at|zig { std.debug.print("{d}:{s}\n", .{ x, text }); }
~tor source {}
! emit string
~proc source|zig { emit("punned!"); }
~source()
! emit |> render-at(x: 5)