[gravity-zero]

Each item has a test proven red before its fix (old code or mutation). Full gate green on be1a691.

Fixes

• E-AC-3: the dec3 lists dependent substreams and their chan_loc (7.1 was announced 6); an AC-3 core is read as AC-3.
• Manifests take an audio track's channel count from the sample entry its init carries (master and init agreed only within the first 128 blocks).
• A Segment of unknown size cut inside a block: diagnose reports truncated (tail), track-ends exits 3 under --exit-damaged.
• A whole Segment of unknown size followed by an ID3 tag or an oversized Void is not cut (to-mp4, to-hls, Fingerprint).
• diagnose --deep-verify on a Segment of unknown size: it runs to the end of the file, body damage is reported.
• Cues past the end of a complete file are a corrupt index (cues-stale, ErrNoKeyframeIndex), not a cut; no false "all cue points reference a non-video track".
• MP4: DeclaredSize walks every top-level box, as Diagnose does.
• Dolby Vision in a Dolby sample entry is named dvh1.PP.LL (dav1, dva1) in CODECS / codecs.
• Cost tests: counted in CI, timed twins nightly (a CPU-only quadratic escapes a count).
• Metadata read and subtitle window cost tests count operations instead of timing.

Features

• Manifests (one set of helpers for every HLS and DASH writer): VIDEO-RANGE, SUPPLEMENTAL-CODECS, CICP properties, CHARACTERISTICS / Role / Accessibility, Atmos (E-AC-3 JOC, also in the dec3), one audio group per codec.
• demux writes each track in its codec's format: ADTS, Annex-B with parameter sets, Ogg Opus / Vorbis, FLAC, .sup; --raw keeps the old output.
• Block additions are read, kept by every rewrite, WebVTT cue settings carried into WebVTT and wvtt; HDR10+ detected from them.
• DASH trick-mode AdaptationSet over the I-frame fragments.

Breaking (see CHANGELOG): bytes served (dec3, channels, HLS masters split by codec, MPD trick-mode set), demux output.

Not covered: VP9 alpha / VP9 HDR10+ in MP4 (no standard carriage), HEVC SEI HDR10+ detection, HLS characteristic for commentary (none defined).