Add MKV muxer, IsoWriter, disc pipeline, and network tests
- MKV muxer: EBML header, segment, cluster, cues, multi-track, keyframe flags — 6 tests
- MkvStream: BD-TS roundtrip, metadata preservation — 2 tests
- IsoWriter: valid UDF, file size update, custom names, empty content — 4 tests
- Disc pipeline: format detection (UHD/BD/DVD), content format, capacity, duration — 5 tests
- Network: listen/connect roundtrip, metadata flow — 2 tests (ignored for CI)
- Encryption: no AACS dir, no keydb — 2 tests
- 297 tests total, all passing
MattJackson
9cb0c369e4