Disc::copy gated its entire mapfile-resume dispatch behind
`if opts.multipass`, so a plain (non-multipass) `disc:// iso://`
copy always called sweep_internal(resume=false) — wiping the
mapfile + ISO and re-sweeping from sector 0. The CLI help and
rip_iso examples promise "auto-resumes if interrupted", and the
sweep already flushes a crash-safe mapfile per block, so the only
missing piece was consulting it on re-run.
Lift the mapfile-resume dispatch out of the multipass guard:
clean->no-op, size-mismatch->fresh sweep, NonTried tail->resume
sweep now apply to both modes. The patch (Pass N) dispatch on
retryable bytes stays multipass-only; a plain copy with a
fully-attempted mapfile returns a terminal result instead of
restarting. autorip (always multipass=true) is unchanged.
Add a regression test that an interrupted plain copy resumes the
NonTried tail and does NOT re-read the Finished prefix.