v0.6.0: Clean API, chipset-keyed profiles, streamlined platform driver

- API: open() is OEM-only, wait_ready() separate, init() optional
- Profiles: chipset-keyed JSON ({ "mt1959": [...], "renesas": [] })
- Profiles: identity group, variant + signature + firmware per drive
- Platform constants: mode, buffer_id, nominal speed, verify commands
  moved from profiles to code (variant-determined, not per-drive)
- Removed unused fields: register CDBs, speed tables, status data
- Platform driver: unlock + firmware upload + calibrate + speed only
- Cross-compile fix: build.rs uses CARGO_CFG_TARGET_OS for framework linking

src/disc.rs

@@ -802,11 +802,9 @@ impl Disc {
             detail: format!("title index {} out of range (have {})", title_idx, self.titles.len()),
         })?;
 
-        // init() already called by DriveSession::open(). No re-init needed.
-
-        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);
+        // Let the drive manage its own read speed after init.
+        // SET_CD_SPEED is only used reactively by the error handler to slow
+        // down on read errors, then let the drive recover.
 
         // Detect kernel max transfer size for this device
         let max_batch = detect_max_batch_sectors(session.device_path());