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.

docs/aacs.md

@@ -189,12 +189,14 @@ In practice, AACS 2.0 UHD discs work through the backward-compatible AACS 1.0 ha
 AACS decryption is transparent to the application. The `Disc::scan()` method handles everything automatically:
 
 ```rust
-use libfreemkv::{DriveSession, Disc};
+use libfreemkv::{Drive, Disc};
 use libfreemkv::disc::ScanOptions;
 use std::path::Path;
 
-let mut session = DriveSession::open(Path::new("/dev/sr0")).unwrap();
-let disc = Disc::scan(&mut session, &ScanOptions::default()).unwrap();
+let mut drive = Drive::open(Path::new("/dev/sg4")).unwrap();
+drive.wait_ready().unwrap();
+drive.init().unwrap();
+let disc = Disc::scan(&mut drive, &ScanOptions::default()).unwrap();
 
 // Check encryption state
 if disc.encrypted {