mux/mp4: M2 — audio tracks + fit oracle (multi-track)

Generalize the sink to N tracks: one video + every MP4-mappable audio
track. Audio sample entries built from the first frame's bitstream —
AC-3 (ac-3/dac3) and E-AC-3 (ec-3/dec3), parsing the (E-)AC-3 BSI for
fscod/bsid/bsmod/acmod/lfeon and the data rate. Per-sample audio
durations from PTS deltas (no reorder → no ctts, all sync). Fit oracle
(mp4_fit_report, exported): video HEVC/H264, audio AC-3/E-AC-3;
TrueHD/DTS/LPCM and bitmap subs are excluded with a typed reason so the
CLI can report exclusions — never a silent drop.

Verified vs ffmpeg -c copy on real discs: AVC+AC3 and HEVC(HDR10)+AC3
both frame-exact on every track (video 2650/4270, audio 5567/3454),
duration and colour identical, clean decode. On a pathological 4-clip
title ffmpeg's OWN output emits the same DTS-monotonicity warnings (more
of them) — source-inherent, not a muxer defect.

src/error.rs

@@ -850,6 +850,11 @@ impl From<Error> for std::io::Error {
             // 9023 MuxEmpty: finish() reached with zero frames — the output
             // would be a header-only container. Treat as invalid output.
             E_MUX_EMPTY => std::io::ErrorKind::InvalidData,
+            // 9048-9050 mp4:// track/codec/config mismatches: the requested
+            // output can't hold this title's video — invalid output request.
+            E_MP4_NO_VIDEO_TRACK | E_MP4_UNSUPPORTED_VIDEO_CODEC | E_MP4_MISSING_CODEC_PRIVATE => {
+                std::io::ErrorKind::InvalidData
+            }
             // 9030 ExtentNotUnitAligned: a malformed/non-AACS-aligned
             // extent was handed to the prefetch producer.
             9030 => std::io::ErrorKind::InvalidInput,