Refactor error types: replace generic AacsError/DiscError with typed variants

- Split AacsError { detail } into 13 specific error variants (AacsCertShort,
  AacsAgidAlloc, AacsCertRejected, etc.) with unique error codes E7001-E7012
- Split DiscError { detail } into 7 specific variants (DiscRead, MplsParse,
  ClpiParse, UdfNotFound, DiscNoTitles, DiscTitleRange, DiscNoExtents)
- Add WriteError (E5001), KeydbLoad (E8005), MuxLookahead (E9000), MuxWrite (E9001)
- Add OpenDisc API for single-call open+scan+rip workflow
- Remove all English text from error Display impl (code-only output)
- Normalize doc comments to use -- instead of em dash for ASCII consistency

src/platform/mt1959/mod.rs

@@ -113,12 +113,7 @@ impl Mt1959 {
 
         if response.len() >= FIRMWARE_ACTIVE_OFFSET + 4
             && response[FIRMWARE_ACTIVE_OFFSET..FIRMWARE_ACTIVE_OFFSET + 4] != FIRMWARE_ACTIVE_SIG {
-            return Err(Error::UnlockFailed {
-                detail: format!(
-                    "mode not active: {:02x}{:02x}{:02x}{:02x}",
-                    response[12], response[13], response[14], response[15]
-                ),
-            });
+            return Err(Error::UnlockFailed);
         }
 
         self.unlocked = true;
@@ -148,9 +143,7 @@ impl Mt1959 {
             match self.do_unlock(scsi) {
                 Ok(_) => { unlocked = true; break; }
                 Err(Error::SignatureMismatch { .. }) => {
-                    return Err(Error::UnlockFailed {
-                        detail: "signature mismatch — wrong profile for this drive".into(),
-                    });
+                    return Err(Error::UnlockFailed);
                 }
                 Err(_) => {
                     let ok = if self.mode == MODE_A {
@@ -163,7 +156,7 @@ impl Mt1959 {
             }
         }
         if !unlocked {
-            return Err(Error::UnlockFailed { detail: "failed after 6 attempts".into() });
+            return Err(Error::UnlockFailed);
         }
         Ok(())
     }

src/platform/mt1959/variant_a.rs

@@ -12,9 +12,7 @@ const VERIFY_BUFFER_ID: u8 = 0x45;
 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(),
-        });
+        return Err(crate::error::Error::UnlockFailed);
     }
 
     // Upload firmware via WRITE_BUFFER

src/platform/mt1959/variant_b.rs

@@ -16,9 +16,7 @@ const VENDOR_VERIFY: [u8; 10] = [0xF1, 0x01, 0x02, 0x00, 0x0D, 0x30, 0x01, 0xF3,
 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(),
-        });
+        return Err(crate::error::Error::UnlockFailed);
     }
 
     // Step 1: Upload firmware via MODE SELECT