Chapters, DVD subtitle palette, MKV track flags, progress total_bytes

Chapters:
- MPLS PlayList marks parsed (mark_type 1 = chapter)
- Chapter struct on DiscTitle (time_secs, name)
- MKV Chapters element with EditionEntry/ChapterAtom per mark
- 3 MPLS mark tests + 2 MKV chapter tests

DVD subtitle palette:
- IFO palette extraction (PGC offset 0xA4, 16 × YCbCr colors)
- YCbCr→RGB conversion for VobSub .idx format
- DvdSubParser codec_private returns formatted palette
- codec_data field on SubtitleStream flows through pipeline
- 5 palette tests (YCbCr conversion, formatting, overflow)

MKV track flags:
- FlagDefault: primary video/audio = 1, secondary = 0
- FlagForced: forced subtitles = 1
- Language: set from stream language code
- Already implemented, verified with 4 new tests

Progress total_bytes:
- IOStream trait: total_bytes() -> Option<u64>
- DiscStream, IsoStream: from disc_title.size_bytes
- M2tsStream, MkvStream: from file metadata on open
- NetworkStream, StdioStream, NullStream: None

316 tests total, all passing.

src/disc/mod.rs

@@ -110,6 +110,8 @@ pub struct DiscTitle {
     pub clips: Vec<Clip>,
     /// All streams (video, audio, subtitle, etc.)
     pub streams: Vec<Stream>,
+    /// Chapter points
+    pub chapters: Vec<Chapter>,
     /// Sector extents for ripping (clip LBA ranges)
     pub extents: Vec<Extent>,
     /// Content format for this title
@@ -190,6 +192,8 @@ pub struct SubtitleStream {
     pub language: String,
     /// Whether this is a forced subtitle
     pub forced: bool,
+    /// Pre-formatted codec private data (e.g. VobSub .idx palette header)
+    pub codec_data: Option<Vec<u8>>,
 }
 
 /// Video/audio codec.
@@ -231,6 +235,15 @@ pub enum ColorSpace {
     Unknown,
 }
 
+/// A chapter point within a title.
+#[derive(Debug, Clone)]
+pub struct Chapter {
+    /// Chapter start time in seconds
+    pub time_secs: f64,
+    /// Chapter name (e.g. "Chapter 1", "Chapter 2")
+    pub name: String,
+}
+
 /// A contiguous range of sectors on disc.
 #[derive(Debug, Clone, Copy)]
 pub struct Extent {
@@ -310,6 +323,7 @@ impl DiscTitle {
             size_bytes: 0,
             clips: Vec::new(),
             streams: Vec::new(),
+            chapters: Vec::new(),
             extents: Vec::new(),
             content_format: ContentFormat::BdTs,
         }
@@ -1073,6 +1087,7 @@ mod tests {
                 secondary: false,
                 label: String::new(),
             })],
+            chapters: Vec::new(),
             extents: Vec::new(),
             content_format: ContentFormat::BdTs,
         }