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/event.rs

@@ -0,0 +1,76 @@
+//! Event system for progress and status reporting.
+//!
+//! The lib fires events during operations like rip().
+//! The app registers a callback to receive them.
+//! No display logic, no English text — just data.
+//!
+//! ```rust
+//! disc.rip(&mut session, 0, output, |event| {
+//!     match event.kind {
+//!         EventKind::BytesRead { bytes, total } => update_progress(bytes, total),
+//!         EventKind::ReadError { sector, .. } => log_error(sector),
+//!         _ => {}
+//!     }
+//! });
+//! ```
+
+use crate::error::Error;
+
+/// An event fired by the lib during operations.
+#[derive(Debug)]
+pub struct Event {
+    pub kind: EventKind,
+}
+
+/// Types of events the lib can fire.
+#[derive(Debug)]
+pub enum EventKind {
+    /// Bytes successfully read and written to output.
+    BytesRead {
+        /// Bytes written so far.
+        bytes: u64,
+        /// Total bytes expected (0 if unknown).
+        total: u64,
+    },
+
+    /// A read error occurred. The lib will retry automatically.
+    ReadError {
+        /// Sector that failed.
+        sector: u64,
+        /// Error code.
+        error: Error,
+    },
+
+    /// Retrying a failed read.
+    Retry {
+        /// Current attempt number (1-based).
+        attempt: u32,
+    },
+
+    /// Drive speed changed (error recovery or restoration).
+    SpeedChange {
+        /// New speed in KB/s (0xFFFF = max).
+        speed_kbs: u16,
+    },
+
+    /// Starting a new disc extent.
+    ExtentStart {
+        /// Extent index (0-based).
+        index: usize,
+        /// First sector of extent.
+        start_sector: u64,
+        /// Number of sectors in extent.
+        sector_count: u64,
+    },
+
+    /// Operation complete.
+    Complete {
+        /// Total bytes written.
+        bytes: u64,
+        /// Total read errors encountered.
+        errors: u32,
+    },
+}
+
+/// A no-op event handler. Ignores all events.
+pub fn ignore(_event: Event) {}