mux: fix DVD subtitle/audio track collision, PGS/VobSub flush, unify TS codec table

Subtitle/DVD output-corruption + stream-mapping coverage fixes.

1. DVD subtitle/audio track-mapping collision (CRITICAL). The PS path
   routed 0xBD private-stream packets to a track via (sub_id & 0x1F)+1,
   so VobSub subtitle sub-id 0x20+j aliased audio track j+1: subtitle
   PES was fed to the AC-3 parser and the real subtitle track got
   nothing. Route by the canonical DVD PID instead via a new
   PsPacket::dvd_pid() that mirrors scan_dvd_titles' PID assignment
   (video 0xE0, audio 0xBD00+i, subtitle 0x20+j), then look up the
   track in pid_to_track. Fixed identically at all three sites
   (pipelined_stream consume_ps, disc.rs live feed, disc.rs EOF flush).
   Unmappable/unmapped packets now WARN instead of silently dropping.

2. PGS flush() missing. PgsParser inherited the no-op default flush, so
   the last subtitle of every PGS track (emitted only when a following
   PCS arrives) was dropped at EOF. Implemented flush() to drain the
   pending display set (duration_ns: None for the trailing block).

3. DVD VobSub multi-PES SPU not reassembled. A subpicture unit larger
   than one PES spans multiple PES (only the head carries a PTS).
   DvdSubParser is now stateful: it buffers per sub-stream until the
   leading 2-byte SPU_size is satisfied, inherits the head PTS, and
   emits one Frame. flush() drains a truncated trailing SPU at EOF.

4. One-table hygiene. scan_streams had a duplicate stream_type->Codec
   table that had drifted from Codec::from_coding_type (missing 0x80
   LPCM, 0x85 mapped to DTS-HD MA vs HR, etc.). scan_streams now uses
   from_coding_type plus a new Codec::kind()/CodecKind category split,
   so the two mappings can never diverge. Silent drops in
   scan_streams and bluray STN parsing now WARN with PID + type.

Tests: dvd_pid mapping + subtitle/audio collision regression, PGS
final-subtitle flush, VobSub multi-PES reassembly + EOF flush,
scan_streams 0x80 LPCM via from_coding_type.

src/mux/pipelined_stream.rs

@@ -124,24 +124,31 @@ impl PipelinedPesStream {
 
     fn consume_ps(&mut self, packets: Vec<super::ps::PsPacket>) {
         for ps in packets {
-            let track = match ps.stream_id {
-                0xE0..=0xEF => 0,
-                0xC0..=0xDF => 1,
-                0xBD => ps
-                    .sub_stream_id
-                    .map(|s| (s & 0x1F) as usize + 1)
-                    .unwrap_or(1),
-                _ => continue,
-            };
-            if track >= self.title.streams.len() {
+            // Route by the REAL DVD PID (matching the PIDs that
+            // `scan_dvd_titles` assigns) rather than a synthetic track
+            // index. The old `(sub_id & 0x1F) + 1` heuristic collided
+            // subtitle sub-id 0x20+j with audio track j+1, feeding
+            // VobSub PES into the AC-3 parser.
+            let Some(pid) = ps.dvd_pid() else {
+                tracing::warn!(
+                    target: "mux",
+                    "dropping unmappable PS packet (stream_id={:#04x}, sub_stream_id={:?})",
+                    ps.stream_id,
+                    ps.sub_stream_id,
+                );
                 continue;
-            }
-            let pid = self
-                .pid_to_track
-                .iter()
-                .find(|(_, idx)| *idx == track)
-                .map(|(p, _)| *p)
-                .unwrap_or(0);
+            };
+            let Some((_, track)) = self.pid_to_track.iter().find(|(p, _)| *p == pid).copied()
+            else {
+                tracing::warn!(
+                    target: "mux",
+                    "dropping PS packet for unmapped PID {:#06x} (stream_id={:#04x}, sub_stream_id={:?})",
+                    pid,
+                    ps.stream_id,
+                    ps.sub_stream_id,
+                );
+                continue;
+            };
             let pes = PesPacket {
                 pid,
                 pts: ps.pts.map(|p| p as i64),