Complete PES pipeline — all streams, clean API

- Unified Stream trait: read() and write() on one type
- PesFrame serialize/deserialize for wire format
- TsDemuxReader: shared BD-TS demux for any Read source
- MkvStream: PES read from MKV (EBML → PesFrame)
- M2tsStream: PES read via TsDemuxReader
- Network/Stdio output: PES serialization directly (no BD-TS wrap)
- Network/Stdio input: deferred (needs PES deserialization protocol)
- TsMuxer for M2TS output from PES frames
- input() and output() functions return Box<dyn Stream>

src/mux/mod.rs

@@ -31,6 +31,7 @@ pub mod mkv;
 pub mod mkvout;
 pub mod pesout;
 pub mod tsmux;
+pub mod tsreader;
 mod mkvstream;
 pub mod network;
 pub mod null;