197 pointfree choke heterogeneous stages

// Pins the point-free choke across a HETEROGENEOUS ladder — the shape every
// real result API has, and the one `analysis` in compiler.kz never exercises
// because it re-raises `| failed` at all six rungs.
//
// Each stage here leaves a DIFFERENT branch unclaimed: obj.get has
// `| not-found`, arr.get has `| out-of-range`, as.string has `| wrong-type`.
// Three dedented chokes claim them; every stage is still left with exactly one
// survivor, so the thread runs the whole ladder.
//
// The rule this pins: a choke replicates onto the stages that DECLARE it, not
// onto every stage. Before the fix, `| out-of-range` was cloned onto obj.get
// and `| not-found` onto arr.get, and the chain died with 8x KORU021 dead
// claims — a chain the survivor logic had already resolved correctly.
//
// Found from the outside: kopium's yyjson delta ladder (koru-examples,
// holes/2_pointfree_choke_replicates_dead_claims) is exactly this shape.
//
// obj.get(2) => 3, arr.get(3) => 4, obj.get(4) => 5, as.string(5) => "deep 5"
~import std/io

~pub tor obj.get { doc: i64, v: i64, key: string }
| found i64
| not-found
~proc obj.get|zig { _ = doc; _ = key; return .{ .found = v + 1 }; }

~pub tor arr.get { doc: i64, v: i64, index: i64 }
| found i64
| out-of-range
~proc arr.get|zig { _ = doc; _ = index; return .{ .found = v + 1 }; }

~pub tor as.string { doc: i64, v: i64 }
| ok string
| wrong-type
// v == 5 only if all three preceding stages actually ran and threaded — the
// whole ladder is under test, not just that it compiled.
~proc as.string|zig {
    _ = doc;
    return .{ .ok = if (v == 5) "deep 5" else "wrong depth" };
}

// `doc` rides every stage explicitly (a value the thread can't carry), so no
// stage goes bare — the collapse is per-stage, exactly as documented.
~pub tor ladder { doc: i64, r: i64 }
| ok string
| gone
~ladder = obj.get(doc, v: r, key: "choices")
  |> arr.get(doc, index: 0)
  |> obj.get(doc, key: "delta")
  |> as.string(doc)
| not-found => gone
| out-of-range => gone
| wrong-type => gone

~ladder(doc: 1, r: 2)
| ok s |> std/io:print.ln("{{ s:s }}")
| gone |> std/io:print.ln("gone")