Add 113 tests, update CI to checkout@v5, add FEATURES.md

Test suite: 64 → 177 tests
- MPLS parser: 6 tests (synthetic binary, streams, errors)
- CLPI parser: 6 tests (EP map, PTS/SPN math, errors)
- H.264: 12 tests (NAL parsing, SPS/PPS, keyframes)
- HEVC: 13 tests (VPS/SPS/PPS, IRAP range, codec private)
- AC3: 12 tests (syncword, frame extraction)
- VC1: 15 tests (BITMAPINFOHEADER, start codes)
- DTS: 5, TrueHD: 4, PGS: 4 tests
- EBML: 6 tests (size/ID/string/float roundtrips)
- UDF: 10 tests (MockSectorReader, filesystem parsing, error paths)
- Disc: 8 tests (scan_image, DiscTitle helpers)
- Streams: 5 new (meta roundtrip, MkvStream)
- NullStream: 4, StdioStream: 2, IsoSectorReader: 2

CI: actions/checkout@v4 → v5 (all workflows)
FEATURES.md: created for v0.7.1

FEATURES.md

@@ -0,0 +1,30 @@
+# libfreemkv — Feature List
+
+## v0.7.1 (current)
+
+### Done
+- [x] Drive access: open, identify, unlock, firmware upload, speed calibration, eject
+- [x] 206 bundled drive profiles (MediaTek MT1959 A + B variants)
+- [x] SCSI transport: Linux SG_IO, macOS IOKit
+- [x] UDF 2.50 filesystem parser (metadata partitions, Blu-ray profile)
+- [x] MPLS playlist parser (play items, STN table, secondary streams)
+- [x] CLPI clip info parser (EP map, sector extents)
+- [x] AACS 1.0 decryption (4 VUK paths: KEYDB, media key, processing key, device key)
+- [x] AACS 2.0 SCSI handshake (P-256/SHA-256 ECDH, bus decryption, read data key)
+- [x] KEYDB.cfg download, verify, save (raw TCP, zero HTTP deps)
+- [x] Content reading with adaptive batch sizing, error recovery, 12+ MB/s
+- [x] Stream labels: 5 BD-J format parsers (Paramount, Criterion, Pixelogic, CTRM, Deluxe)
+- [x] MKV muxer: 8 codec parsers (H.264, HEVC, AC-3, DTS, TrueHD, PGS, VC-1, LPCM)
+- [x] SectorReader trait: decouples disc scanning from SCSI
+- [x] 7 stream types: Disc, ISO, MKV, M2TS, Network, Stdio, Null
+- [x] IOStream trait with URL-based resolver (scheme://path)
+- [x] FMKV metadata header for M2TS and network streams
+- [x] Numeric error codes only (no English text in library)
+- [x] Event system for progress callbacks
+
+### Planned
+- [ ] Windows SCSI transport (SPTI)
+- [ ] Pioneer Renesas platform support (48 drives, need GET_CONFIG 010C)
+- [ ] DVD CSS decryption
+- [ ] TranscodeStream (ffmpeg integration)
+- [ ] ISO write with BD-compliant UDF structure