The sampler and the workdir-relative display conversion group by
node:path.sep, so the POSIX-style '/' literals in the cross-directory
sampling cases collapse into per-path groups on Windows (every path its
own top-level entry), turning the round-robin sample into a head. The
same gap exists on master (its platform-separator fix predates these
tests); normalize the literals through a platform helper instead, and
keep the POSIX-backslash-as-filename case Windows-skipped as before.