Remove SpeedTable, add probe_disc(), named constants, clean architecture

- Removed SpeedTable entirely — drive manages speeds after probe
- Renamed read_speed_table() → probe_disc()
- Named all SCSI constants: SUB_CMD_UNLOCK, SUB_CMD_INIT, SUB_CMD_PROBE,
  INIT_ADDR_BD, INIT_ADDR_UHD, PROBE_COARSE_END, PROBE_FINE_END, etc.
- Auto-detect BD vs UHD from disc capacity for correct probe init address
- Fixed NOMINAL_SPEED_B (was invalid CDB, removed — single max instead)
- Added session.set_speed() for simple speed control
- Error recovery: re-init on first error, BD2x on repeated errors
- Batch size uses full kernel limit (was 80%, now 100%)
- Clean variant_a/variant_b with named constants

API: open() → wait_ready() → init() → probe_disc() → scan() → read

README.md

@@ -29,8 +29,9 @@ use std::path::Path;
 
 // Open drive — profiles are bundled, auto-identified
 let mut session = DriveSession::open(Path::new("/dev/sr0"))?;
-session.wait_ready()?;        // wait for disc
-session.init()?;               // optional: unlock + calibrate for full speed
+session.wait_ready()?;            // wait for disc
+session.init()?;                   // unlock + firmware upload
+session.probe_disc()?;             // probe disc surface for optimal speeds
 
 // Scan disc — UDF, playlists, streams, AACS (all automatic)
 let disc = Disc::scan(&mut session, &ScanOptions::default())?;