Source read via streamed vault open + bounded staging copy (index-only duration/extension); encoded output walked from a bounded stream (new OggOpusParser.WalkAsync, byte-identical to the buffer oracle) and stored via streaming vault write. Adds parity tests.
Player picks Opus when the browser can decode it and a sidecar exists (else lossless), injecting the sidecar before stream init; seek reuses the same format. Adds the Backfill-Opus bulk API endpoint + CMS action.
Background-job transcode (ffmpeg/libopus) after source store; pure C# Ogg
walker builds the 0.5s-bucketed granule→byte seek index + captures the
OpusHead/OpusTags setup header into a per-track sidecar in a new track-opus
vault. Best-effort, additive, regenerated on replace-audio.
daniel-c-harvey