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/mpls.rs

@@ -62,17 +62,17 @@ pub struct StreamEntry {
 /// Parse an MPLS file from raw bytes.
 pub fn parse(data: &[u8]) -> Result<Playlist> {
     if data.len() < 40 {
-        return Err(Error::DiscError { detail: "MPLS too short".into() });
+        return Err(Error::MplsParse);
     }
     if &data[0..4] != b"MPLS" {
-        return Err(Error::DiscError { detail: "not an MPLS file".into() });
+        return Err(Error::MplsParse);
     }
 
     let version = String::from_utf8_lossy(&data[4..8]).to_string();
     let playlist_start = u32::from_be_bytes([data[8], data[9], data[10], data[11]]) as usize;
 
     if playlist_start + 10 > data.len() {
-        return Err(Error::DiscError { detail: "MPLS playlist offset out of range".into() });
+        return Err(Error::MplsParse);
     }
 
     let pl = &data[playlist_start..];