100% codec coverage + disc/ and aacs/ module refactors

Codec coverage (DVD + BD + UHD):
- E-AC-3 (Dolby Digital Plus): bsid detection, frame size calc — 8 tests
- DTS-HD MA/HR: extension substream (0x64582025) detection — 8 tests
- LPCM: BD header skip, raw PCM extraction — 6 tests
- DVD VobSub subtitles: passthrough parser — 5 tests
- Dolby Vision: verified RPU NAL type 62 preserved in HEVC — 1 test

Module refactors:
- disc.rs → disc/mod.rs + bluray.rs + dvd.rs + encrypt.rs
- aacs/mod.rs (1661 lines) → mod.rs (21) + keydb.rs + keys.rs + decrypt.rs
- All public APIs preserved, all tests pass

270 tests total, 0 failures.

src/mux/codec/dvdsub.rs

@@ -0,0 +1,103 @@
+//! DVD bitmap subtitle (VobSub) parser.
+//!
+//! DVD subtitles are carried in PS private stream 1 with sub-stream IDs 0x20-0x3F.
+//! Each subtitle display set may span multiple PES packets, but at the MKV level
+//! we pass through the raw VobSub packets as-is — the container wraps them.
+//!
+//! For MKV: codec ID "S_VOBSUB".
+//! All frames are keyframes (each is a complete bitmap).
+
+use super::{pts_to_ns, CodecParser, Frame, PesPacket};
+
+pub struct DvdSubParser;
+
+impl Default for DvdSubParser {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl DvdSubParser {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl CodecParser for DvdSubParser {
+    fn parse(&mut self, pes: &PesPacket) -> Vec<Frame> {
+        if pes.data.is_empty() {
+            return Vec::new();
+        }
+        let pts_ns = pes.pts.map(pts_to_ns).unwrap_or(0);
+        vec![Frame {
+            pts_ns,
+            keyframe: true,
+            data: pes.data.clone(),
+        }]
+    }
+
+    fn codec_private(&self) -> Option<Vec<u8>> {
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::mux::ts::PesPacket;
+
+    fn make_pes(data: Vec<u8>, pts: Option<i64>) -> PesPacket {
+        PesPacket {
+            pid: 0x1200,
+            pts,
+            dts: None,
+            data,
+        }
+    }
+
+    #[test]
+    fn passthrough_data() {
+        let mut parser = DvdSubParser::new();
+        let sub_data = vec![0x00, 0x0A, 0x00, 0x08, 0x01, 0xFF, 0x02, 0x03, 0x04, 0x05];
+        let pes = make_pes(sub_data.clone(), Some(90000));
+        let frames = parser.parse(&pes);
+
+        assert_eq!(frames.len(), 1);
+        assert_eq!(frames[0].data, sub_data, "VobSub data should pass through unmodified");
+        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+    }
+
+    #[test]
+    fn always_keyframe() {
+        let mut parser = DvdSubParser::new();
+        for i in 0..3u8 {
+            let data = vec![0x00, i, 0x00, i + 1];
+            let pes = make_pes(data, Some(90000 * i as i64));
+            let frames = parser.parse(&pes);
+            assert_eq!(frames.len(), 1);
+            assert!(frames[0].keyframe, "DVD subtitle frames should always be keyframes");
+        }
+    }
+
+    #[test]
+    fn empty_pes_returns_no_frames() {
+        let mut parser = DvdSubParser::new();
+        let pes = make_pes(Vec::new(), Some(0));
+        assert!(parser.parse(&pes).is_empty());
+    }
+
+    #[test]
+    fn codec_private_none() {
+        let parser = DvdSubParser::new();
+        assert!(parser.codec_private().is_none());
+    }
+
+    #[test]
+    fn no_pts_defaults_to_zero() {
+        let mut parser = DvdSubParser::new();
+        let pes = make_pes(vec![0x01, 0x02], None);
+        let frames = parser.parse(&pes);
+        assert_eq!(frames.len(), 1);
+        assert_eq!(frames[0].pts_ns, 0);
+    }
+}