019 arm produces a bare return record

// Pins that an arm producing into a BARE-RETURN tor emits the value itself.
//
// A produce inside an arm was always lowered as a named-branch constructor:
// `-> finished d` becomes `.{ .finished = d }`. A bare-return tor has no branch
// to name, and the emitter wrote the wrapper anyway — `.{ . = { label: "high",
// code: 1 } }`. A field access with an empty name, AND the Koru record pasted
// through untranslated, because the wrapper had swallowed the one path that
// lowers it. Two errors from one missing question.
//
// Mirror of 350_017, which fixed the same blind spot from the other side: there
// a NAMED produce was lowered as if it were bare. Every wall guards one
// direction of a symmetry.
//
// This is the shape every route handler in orisha has — its `handler` returns a
// bare record and its router arms produce one.

~import std/io

~tor pick { n: i32 }
| high
| low

~proc pick|zig {
    return if (n > 5) .high else .low;
}

~tor classify { n: i32 } -> { label: string, code: i32 }

~classify =
    pick(n)
    | high -> { label: "high", code: 1 }
    | low -> { label: "low", code: 0 }

~classify(n: 9): a |> std/io:print.ln("{{ a.label:s }}/{{ a.code:d }}")
~classify(n: 2): b |> std/io:print.ln("{{ b.label:s }}/{{ b.code:d }}")