137 effect unit payload spelled by omission

// A payload-less effect branch is spelled by OMISSION — `! ask | halved i32
// | timeout` — never with a unit token. `()` is not a type in the decl
// grammar; without this wall it parses as an identity payload whose type
// string is literally "()" and dies three stages later as a misleading
// KORU030. The unit exists only on the VALUE side: the proc calls `ask()`
// positionally. (Ruled 2026-07-01: omission is the one spelling; no synonym.)
~pub event request { payload: i32 }
! ask () | halved i32 | timeout
| done i32

~proc request|zig {
    const r = ask();
    return switch (r) {
        .halved => |v| .{ .done = v },
        .timeout => .{ .done = -1 },
    };
}