test(hls): [PKG-HLS-02] cover released contracts and real SDK playback

test/browser/media/hls/README.md

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+# Deterministic HLS fixtures
+
+Generated by `node scripts/generate-hls-fixture.mjs`, using FFmpeg recorded in manifest.json.
+No downloaded film or audio: testsrc2 supplies moving patterns, sine supplies 440/880 Hz audio.
+The 12-second master offers 160x90 and 320x180 AVC video, English/French AAC audio, and a
+separate video-only master for topology changes. Each media playlist is VOD with 2-second segments.
+
+Segments use `.mpegts` so source tools cannot mistake MPEG transport streams for TypeScript.
+The HLS browser fixture serves them as video/mp2t. File contents and byte counts are checked
+against manifest.json before browser use. Tests need neither FFmpeg nor a remote media service.
+
+To change the media, generate into a new directory, for example
+`node scripts/generate-hls-fixture.mjs refactor/.cache/hls-media-next`; inspect the output and
+update the media, manifest and browser evidence together. The script refuses existing directories.
+Set ARTPLAYER_FFMPEG to a particular FFmpeg executable if it is not on PATH. Re-encoding with
+another FFmpeg version is not expected to preserve bytes; do not overwrite hashes to silence drift.