DiscStream::fill_extents loops internally while the demuxer waits for
enough clean data to emit a PES frame. In a dense bad zone that loop
can run for minutes without returning to the outer read() call, so
the caller's Stop signal never gets serviced until a frame is finally
emitted — which may be very far away.
Add DiscStream::set_halt(Arc<AtomicBool>) — typically wired to
Drive::halt_flag() for unified Stop across drive recovery phases and
stream sector processing. fill_extents checks the flag at the top of
every retry iteration; raising it returns Err(Error::Halted) within
one SCSI round-trip.
No behavior change for callers that don't call set_halt. Unblocks the
architectural fix for the "Stop doesn't stop" bug observed on a
damaged UHD disc.
Replace read_with_binary_search + 3×5s light recovery with an adaptive
sizer that shrinks on failure (halve, 3-aligned ≥6) and probes back up
after 100 MiB (51,200 sectors) of clean reads. Descent cost is paid
once per bad region, not once per bad sector.
Emit BatchSizeChanged { new_size, reason } on shrink and probe-up.
Remove BinarySearch event — no longer produced.
Side fix: scsi/macos.rs one-liner for manual_c_str_literals clippy
lint that surfaced on a newer toolchain.
matthew