v0.10.1: Streams are PES, Disc::copy() for sector dumps, zero English

Architecture:
- One stream per format, bidirectional PES (read/write on same type)
- IsoStream merged into DiscStream (one type, any SectorReader)
- Disc::copy() for disc→ISO raw sector dump
- IOStream trait deleted, all byte-level Read/Write removed
- ContentReader/OpenDisc/open_title/open_input/open_output deleted
- CountingStream wrapper for progress tracking

Error codes:
- All io::Error English strings replaced with Error enum variants
- From<Error> for io::Error conversion
- Unused variants removed, new stream/mux variants added

Deleted: mkvout.rs, pesout.rs, isowriter.rs, mkv-muxer-plan.md
Updated: all docs, README stream table, CHANGELOG

238 tests, 0 clippy warnings.

src/drive/mod.rs

@@ -141,8 +141,8 @@ impl Drive {
             }
             std::thread::sleep(std::time::Duration::from_millis(500));
         }
-        Err(Error::DeviceNotFound {
-            path: format!("{}: drive not ready after 30s", self.device_path),
+        Err(Error::DeviceNotReady {
+            path: self.device_path.clone(),
         })
     }
 
@@ -264,8 +264,8 @@ impl Drive {
             }
         }
 
-        Err(Error::DeviceNotFound {
-            path: format!("{}: drive reset failed", self.device_path),
+        Err(Error::DeviceResetFailed {
+            path: self.device_path.clone(),
         })
     }