1.6.0: remove recovery strategy (moved to freemkv-engine) + trim dead surface

The sweep/patch recovery strategy, mapfile, retry-decision state machine,
section-recover, and damage classification move out of libfreemkv into the
new freemkv-engine crate. libfreemkv keeps the raw single-shot read and
SCSI-fact translation (SenseFamily stays in scsi).

- Delete disc/{sweep,patch,mapfile,read_error,section_recover}.rs, the
  Disc::copy/sweep/patch methods, the Copy/Sweep/Patch option+result types,
  classify_damage/DamageSeverity, progress_snapshot_from_mapfile, and the
  three recovery integration tests.
- Trim public surface the recovery deletion orphaned: delete the dead
  READ_PIPELINE_DEPTH const, the write-side SectorSink/FileSectorSink (no
  consumer), and the DriveSpeed enum (its one live use — set max drive
  speed — becomes Drive::SPEED_MAX_KBPS). Make mapfile_path_for,
  decrypt_sectors_mapped pub(crate); gate NoopEvents to test.
- Version 1.6.0.

src/decrypt.rs

@@ -381,7 +381,7 @@ impl AacsKeyMap {
 /// decorator can dispatch uniformly. A map index outside the held pool is a
 /// fail-loud [`Error::DecryptFailed`]: the resolver's job is to guarantee every
 /// selectable index is present, so a gap here is a resolver bug, not silent loss.
-pub fn decrypt_sectors_mapped(
+pub(crate) fn decrypt_sectors_mapped(
     buf: &mut [u8],
     keys: &DecryptKeys,
     base_lba: u32,