DriveProfile with all per-drive fields, drive.rs uses init() as single entry

DriveProfile now has every field traced from firmware:
- drive_signature, unlock_init_value, unlock_response_size_minus_init
- ld_microcode (base64, ~1888B firmware payload)
- hardware_register_a_cdb, hardware_register_b_cdb (10B pre-built CDBs)
- drive_nominal_speed_cdb (12B calibration speed)
- speed_zone_table (28B), speed_calc_table (25B)

drive.rs simplified:
- open() calls init() instead of unlock()
- init() is the ONLY entry point — handles full dispatch sequence internally
- Removed read_config, read_register, maintain_speed, read_sectors from public API
- Added set_read_speed() for per-zone speed during content reads
- disc.rs updated to call init() instead of unlock()

Compiles clean, all tests pass.

src/disc.rs

@@ -793,12 +793,10 @@ impl Disc {
             detail: format!("title index {} out of range (have {})", title_idx, self.titles.len()),
         })?;
 
-        // Try to unlock for raw reads. Non-fatal — BD discs work without unlock.
         if !session.is_unlocked() {
-            let _ = session.unlock();
+            let _ = session.init();
         }
 
-        // Set max read speed — nothing else. No calibration, no probes.
         let speed_cdb = crate::scsi::build_set_cd_speed(0xFFFF);
         let mut dummy = [0u8; 0];
         let _ = session.scsi_execute(&speed_cdb, crate::scsi::DataDirection::None, &mut dummy, 5_000);