Speed table: generic zone-based speed management

- SpeedTable: maps disc positions to optimal speeds
- Default: max speed everywhere (drive manages itself)
- After read_speed_table(): calibrated per-zone speeds
- One u32 comparison per read on hot path
- Error recovery: reduce() / resume() override table temporarily
- Replaces old tier-based speed management in ContentReader
- MT1959 split into mod.rs + variant_a.rs + variant_b.rs
- PlatformDriver: init() + read_speed_table() + is_ready()

src/platform/mt1959/variant_a.rs

@@ -0,0 +1,33 @@
+//! MT1959 variant A firmware upload.
+
+use crate::error::Result;
+use crate::scsi::{DataDirection, ScsiTransport};
+use super::Mt1959;
+
+pub(super) fn load_firmware(mt: &mut Mt1959, scsi: &mut dyn ScsiTransport) -> Result<()> {
+    let firmware = &mt.profile.firmware;
+    if firmware.is_empty() {
+        return Err(crate::error::Error::UnlockFailed {
+            detail: "no firmware in profile".into(),
+        });
+    }
+
+    let len = firmware.len();
+    let cdb = [
+        0x3B, 0x06, 0x00,
+        0x00, 0x00, 0x00,
+        (len >> 16) as u8, (len >> 8) as u8, len as u8,
+        0x00,
+    ];
+    let mut data = firmware.clone();
+    scsi.execute(&cdb, DataDirection::ToDevice, &mut data, 30_000)?;
+
+    // Verify (may fail, non-fatal)
+    let verify_cdb = [0x3C, 0x01, 0x45, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00];
+    let mut verify_resp = [0u8; 4];
+    let _ = scsi.execute(&verify_cdb, DataDirection::FromDevice, &mut verify_resp, 5_000);
+
+    mt.do_unlock(scsi)?;
+    mt.do_unlock(scsi)?;
+    Ok(())
+}