fix: preserve all returns when trailing bool is a flag

[ivov]

bytes.Cut, strings.Cut, go/types.LookupFieldOrMethod, and golang.org/x/sync/singleflight.Group.Do now return their full N-tuple rather than collapsing to Option<(T, U)>. The trailing bool on these functions is metadata, not a presence flag, so the prior shape silently discarded values on the most common code path.

import "go:strings"

let (before, after, found) = strings.Cut("hello:world", ":")
if found {
  fmt.Println(before, after)
}

[github-actions]

Released in lisette-v0.2.0