Add MKV muxer and event system

- Add event.rs: structured event system for progress reporting
- Add mux/: MKV muxer pipeline (EBML writer, TS demuxer, stream assembly)
  - Codec parsers: H.264, HEVC, AC-3, DTS, TrueHD, PGS, VC-1
  - Lookahead buffer for codec private data extraction
  - Direct m2ts-to-MKV streaming without intermediate files

src/mux/mod.rs

@@ -0,0 +1,25 @@
+//! MKV muxing pipeline.
+//!
+//! Provides BD transport stream → MKV remuxing via composable streams.
+//!
+//! The main type is `MkvStream` — wraps any `Write + Seek` output,
+//! receives raw BD-TS bytes via `write()`, outputs MKV.
+//!
+//! ```text
+//! disc.rip(title, MkvStream::new(file, &title))
+//! ```
+//!
+//! Components (for advanced use):
+//! - `ts`: BD transport stream demuxer (192-byte packets → PES frames)
+//! - `ebml`: EBML write primitives for Matroska container
+//! - `mkv`: MKV muxer (tracks, clusters, blocks, cues)
+//! - `codec`: Elementary stream parsers (frame boundaries, codec headers)
+
+pub mod ebml;
+pub mod ts;
+pub mod mkv;
+pub mod codec;
+pub mod lookahead;
+pub mod stream;
+
+pub use stream::MkvStream;