disc: DiscRead carries SCSI status/sense

Fix extract_scsi_context() and Error::scsi_sense() to handle Error::DiscRead
in addition to Error::ScsiError, so is_marginal_read() works for DiscRead
errors and disc::copy() can properly route MEDIUM ERROR as a marginal
(bad sector) instead of bailing.

Closes: freemkv-private#20260427

src/drive/mod.rs

@@ -5,6 +5,7 @@
 pub(crate) fn extract_scsi_context(e: &Error) -> (u8, Option<crate::scsi::ScsiSense>) {
     match e {
         Error::ScsiError { status, sense, .. } => (*status, *sense),
+        Error::DiscRead { status, sense, .. } => (status.unwrap_or(0), *sense),
         _ => (0, None),
     }
 }

src/error.rs

@@ -490,6 +490,7 @@ impl Error {
     pub fn scsi_sense(&self) -> Option<&crate::scsi::ScsiSense> {
         match self {
             Error::ScsiError { sense: Some(s), .. } => Some(s),
+            Error::DiscRead { sense: Some(s), .. } => Some(s),
             _ => None,
         }
     }