v0.13.44: macOS raw CDB transport via IOKit exclusive access

macOS SCSI transport rewritten from hybrid MMC+pread to single-path
raw CDB dispatch through SCSITaskDeviceInterface. All CDBs (INQUIRY,
READ, REPORT KEY, etc.) now go through ExecuteTaskSync — 1:1 with
the Linux SG_IO backend.

Key changes:
- New macos_shim.c: diskutil unmount → find IOBDServices →
  ObtainExclusiveAccess → raw CDB dispatch. Eliminates Rust-side
  IOKit COM vtable complexity.
- build.rs compiles macos_shim.c via cc into static lib
- macos.rs simplified to three FFI calls (open/close/execute)
- disc/mod.rs: graduated batch restore after errors, skip-ahead
  through bad zones, configurable error pause

src/scsi/mod.rs

@@ -2,7 +2,7 @@
 //!
 //! Platform backends are in separate files:
 //!   - `linux.rs` — SG_IO ioctl
-//!   - `macos.rs` — IOKit SCSITaskDeviceInterface
+//!   - `macos.rs` — IOKit SCSITaskDeviceInterface (exclusive access)
 //!   - `windows.rs` — SPTI (SCSI Pass-Through Interface)
 
 #[cfg(target_os = "linux")]